Law
of Motion
Q.1 A man is pulling on a rope attached to a block on a
smooth horizontal surface. The tension in the rope will be the same at all of
its points–
(a) if and only if the rope is not accelerating
(b) if and only if the rope is massless
(c) if and only if the rope is massless and not accelerating
(d) if either the rope is massless or not accelerating
Q.2 A
block of mass M is pushed along a
horizontal surface by a rope of mass m.
Force F is applied at one end of the
rope. The force which the rope exerts on the block is
(a) FM / (M – m) (b) FM
/ (M + m)
(c) Fm / (M + m) (d) Fm (M
- m)
Q.3 A 45kg load is being pulled vertically by a rope
whose breaking strength is 495N. With what maximum acceleration the load can be
pulled up? (g = 10m/s2)
(a) 11m/s2 (b) 10m/s2 (c) 1m/s2 (d) 21m/s2
Q.4 With what minimum acceleration can a fireman slide
down a rope where breaking strength is two – thirds of its weight?
(a) 2/3g (b) g (c) 1/3g (d) zero
Q.5 A body of mass 0.1kg is suspended from a massless
string. The point of suspension moves (I)
up (ii) down with an acceleration of
5m/s2. If the tension in newtons in the string in the two cases are T1 and T2 respectively, then
(a) T1 = T2 (b) T2 - T1
= 1
(c) T1 - T2 = 1 (d) T1
- T2 = 2
Q.6 If the tension in the cable of
100kg elevator is 1000kg weight, the elevator
(a) is accelerating upwards (b) is accelerating downwards
(c)
may be at rest or
accelerating
(d) may
be at rest or in uniform motion.
Q.7 Two masses of 10kg and 20kg respectively are
connected by a massless spring kept on a horizontal smooth table. A force of
200N acts on the 20kg mass. At a given instant if the 10kg mass has an
acceleration of 12m/s2. What is the acceleration of 20kg mass?
(a) zero (b) 10m/s2 (c) 4m/s2 (d) 12m/s2
Q.8 A 2kg mass pulls horizontally on a 3kg mass by means
of a lightly stretched spring. If at one instant the 3kg mass has an
acceleration towards 2kg mass 0f 1.8m/s2, the acceleration of 2kg
mass is
(a) 1.2 m/s2 (b) 3.6 m/s2 (c) 2.7 m/s2 (d) zero
Q.9 An elevator starts from rest with a constant upwards
acceleration. It moves 2.0m in the first 0.5s. A passenger in the elevator is
holding a 3kg package by a vertical spring. The tension in the spring is (Take
g = 10m/s2)
(a) 36N (b) 8N (c) 30N (d) 48N
Q.10 Two masses 2kg and 1kg are connected by an
inextensible string passing over a smooth fixed pulley. The pressure in kg-wt
on the axle of the pulley is
(a) 3kg.wt (b) 1.5kg.wt
(c) more than 3kg.wt (d) less than 3kg.wt
Q.11 When a body is stationary :
(a)
there is no force
acting on it
(b)
the forces acting on
it are not in contact with it
(c)
the combination of
forces acting on it balances each other
(d)
the body is in vacuum
Q.12 When
a body is in translatory equilibrium :
(a)
the body is
definitely at rest
(b)
the body is
definitely in the state of uniform motion
(c)
the body will be
either at rest or in the state of uniform motion
(d)
none of the above
Q.13 A body of mass 40 kg is hanging
from the horizontal branch of a tree. The tension in his arms is minimum when
the angle between the arms is :
(a) 0° (b) 90° (c) 120° (d) 180°
Q.14 If a force
of 250 N acts on a body, the momentum required is 125 m/s, what is the period
for which force acts on the body?
(a) 0.2 sec (b) 0.5 sec
(c) 125 ´ 250 sec (d) 0.25 sec
Q.15 A man is
rest in the middle of a pond on perfectly smooth ice. He can get himself to the
shore by making use of Newton’s :
(a) first law (b) second law (c) third law (d) all the news.
Q.16 An elevator
is moving vertically upwards with an acceleration of 6 m/s-2 ; the
force exerted on the floor by the man of mass 70 kg is :
(a) 420 N (b) 70(6 + 9.8)N
(c) 70 (-6 + 9.8)N (d) 70 ´ 9.8 N.
Q.17 A balloon has 8 gram of air. A
small hole is pierced into it. The air escapes at a uniform rate of 7 cms-1.
If the balloon shrinks in 5.6 seconds then the average force acting on the
balloon is :
(a) 10-4
N (b) 10-2 dyne
(c) 56 dyne (d) 10-6 dyne.
Q.18 A toy of mass 1 kg is placed on a
spring balance. Suddenly, the toy jumps upwards. When it happens, the reading
of the spring balance changes from 1 kg to 1.10 kg. What will be the maximum
value of the upward acceleration of the toy? Take g = 10 ms-2.
(a) 1 ms-2 (b) 0.1 ms-2
(c) 0.01 ms-2 (d) 0.001
ms-2.
Q.19 A rocket of
mass 120 kg is fired in the gravity free space. It ejects gases with velocity
600 ms-1 at the rate of 1 kg/s. What will be the initial
acceleration of the rocket?
(a) 1 ms-2 (b) 5 ms-2 (c) 10 ms-2 (d) 15
ms-2.
Q.20 A machine gun is mounted on a
2000 kg vehicle on a horizontal smooth road (friction negligible). The gun
fires 10 bullets per sec with a
velocity of 500 m/s. If the mass of each bullet be 10g, what is the acceleration
produced in the vehicle?
(a) 25 cm/s2 (b) 25
m/s2 (c) 50 cm/s2 (d) 50 m/s2.
Q.21 A body of mass M is acted upon by
a force F and the acceleration produced is a. If there forces each equal to F
and inclined to each other at 120° act on the same body, the acceleration produced
will be :
(a) Ö2a (b) a/Ö3 (c) 3a (d) zero.
Q.22 A packet of weight W is dropped
with the help of a parachute and on striking the ground comes to rest with a
retardation equal to twice the acceleration due to gravity. What is the force
exerted on the ground?
(a) W (b) 2W (c) 3W (d) 4W.
Q.23 A dish of mass 10 g is kept
floating horizontally in the air by firing bullets each of mass 5g with the
same velocity. If 10 bullets are fired per second and the bullets rebound with
the same velocity, then the velocity of each bullet is :
(a) 196 cm/sec (b) 98
cm/sec
(c) 49 cm/sec (d) none of
these.
Q.24 An object is resting at the
bottom of two strings which are inclined at angle of 120° with each other. Each string can
withstand a tension of 20 N. The maximum weight of the object that can be
sustained without breaking the string is :
(a) 10 N (b) 20 N (c) 20Ö2 N (d) 40
N.
Q.25 A wagon weighing 1000 kg is
moving with velocity 50 km/h on smooth horizontal rails. A mass of 250 kg is
dropped into it. The velocity with which it moves now is :
(a) 12.5
km/h (b) 20 km/h
(c) 40 km/h (d) 50
km/h.
Q.26 A gun of mass 10 kg fires 4
bullets per seconds. The mass of each bullet is 20 kg and the velocity of the
bullet when it leaves the gun is 300 ms-1. The force required to
hold the gun when firing is :
(a) 6 N (b) 8 N (c) 24 N (d) 40 N.
Q.27 Bullets of 0.03 kg mass each hit
a plate at the rat of 200 bullets per second, with a velocity of 50 m/sec and
reflect back with a velocity of 30 ms-1. The average force acting on
the plane in Newton is :
(a) 120 (b) 180 (c) 300 (d) 480.
Q.28 A ball of mass 0.5 kg moving with
a velocity of 2ms-1 strikes a wall normally and bounces back with
the same speed. If the time of contact between the ball and the wall is 10-3
sec, the average force exerted by the wall on the ball is :
(a) 1125 N (b) 1000 N (c) 500 N (d) 2000 N.
Q.29 A 4000 kg rocket is set for
firing. If the exhaust speed is 1000 ms-1, the mass to be ejected
per second to just overcome gravitational pull (g = 10 ms-2) is
:
(a) 20 kg (b) 10 kg (c) 5 kg (d) 40 kg.
Q.30 A truck, weighing 8000 kg, is
moving along a track with negligible friction at 1.8 ms-1 with the
engine turn off when it begins to rain hard. The raindrops fall vertically with
respect to the ground. The speed of the truck, when it has collected 1000 kg of
rain water, is :
(a) 1.6 ms-1 (b) 10 ms-1 (c) 3ms-1 (d) 9 ms-1.
Law
of Motion
1.
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(d)
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2.
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(b)
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3.
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(c)
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4.
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(c)
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5.
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(c)
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6.
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(d)
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7.
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(c)
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8.
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(c)
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9.
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(b)
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10.
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(d)
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11.
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(c)
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12.
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(c)
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13.
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(a)
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14.
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(b)
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15.
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(c)
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16.
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(b)
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17.
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(a)
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18.
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(a)
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19.
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(b)
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20.
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(a)
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21.
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(d)
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22.
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(c)
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23.
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(b)
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24.
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(b)
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25.
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(c)
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26.
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(c)
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27.
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(d)
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28.
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(d)
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29.
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(d)
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30.
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(a)
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FRICTION
Q.1 A uniform chain of length l lies on a rough table with coefficient of friction m. What maximum portion of its
length can overhang from the edge of the table without sliding down?
(a) l / m (b) l / m+1 (c) l / m+1l (d) l
/ m -1 l
Q.2 A block of mass 2kg rests on a rough inclined plane
making an angle of 30° with the horizontal.
The coefficient of static friction between the block and the plane is 0.7. The
frictional force on the block is
(a) 9.8N (b) (0.7)
(9.8) (Ö3)N
(c) (9.8)Ö3N (d) (0.7)
(9.8) N
Q.3 A given body takes n times as much time to slide down a 45° rough incline as it takes to
slide down a perfectly smooth 45°incline. The coefficient of kinetic friction between
the body and the incline is given by
(a) [1- 1/n2] (b) 1/ [1- n2] (c) Ö[1- 1/n2] (d) Ö[1/1-n2]
Q.4 A block of mass 0.1 kg is held
against a wall by applying a horizontal force of 5N on the block. If the
coefficient of friction between the block and the wall is 0.5, the magnitude of
the frictional force acting on the block is
(a) 2.5N (b) 0.98N (c) 4.9N (d) 0.49N
Q.5 Of the following forces of friction, the one which
is self-adjusting is :
(a) rolling friction (b) sliding friction
(c) static friction (d) rolling friction
Q.6 The
maximum static frictional force depends on :
(a)
area of surfaces in
contact (b) normal
reaction
(c) direction of applied force (d) none of the above
Q.7 The
static friction is:
(a)
equal to the dynamic
frication
(b)
always less than the
dynamic friction
(c)
always greater than
the dynamics friction
(d)
sometimes greater and
sometimes equal to dynamic friction
Q.8 If
the normal reactional force is doubled, the coefficient of friction is :
(a) doubled (b) halved (c) not changed (d) tripled
Q.9 Which
of the following statements is false?
(a)
Force of friction is
independent of macroscopic area of the surface in contact
(b)
Force of friction
depends on the nature of materials of the surfaces in contact (i.e., force of
adhesion)
(c)
Force of friction
does not depends on the rela5tive velocity between the surfaces
(d)
Force of friction is
independent of roughness or smoothness of the surfaces in contact
Q.10 Friction
:
(a)
does not affect the
efficiency of a machine
(b)
increases the
efficiency of a machine
(c)
decreases the
efficiency of a machine
(d)
noting can be said
about the effect of friction on efficiency of a machine
Q.11 Friction
:
(a)
always opposes the
motion of a moving body
(b)
may cause the motion
of the body
(c)
is a conservative
force
(d)
none of the above
Q.12 The frictional force between two surfaces is
independent of :
(a) nature
of surface` (b) size of
the body
(c) area of contact (d) mass of the body
Q.13 A block mass 2 kg is placed on
the floor. The coefficient of static friction is 0.4. If a force of 2.8 N is
applied on the block parallel to the floor, the force of friction between the
block and floor (taking g = 10 ms-2) is :
(a) 2.8 N (b) 8 N (c) 2 N (d) zero
Q.14 A block has been placed on an
inclined plane. The slope angle q of the plane is such that the block slides down the
plane at a constant speed. The coefficient of kinetic friction is equal to
:
(a) sin q (b) cos q (c) g (d) tan q
Q.15 If mk is the coefficient of kinetic friction, mf the coefficient of rolling
friction and ms the coefficient of static
friction then generally :
(a) ms > mk > mr
(b) ms < mk < mr
(c) ms < mk > mr
(d) ms > mr > mk
Q.16 A block of 10 kg is pulled by a
constant speed on a rough horizontal surface by a force of 19.6 N. The
coefficient of friction is :
(a) 0.1 (b) 0.2 (c) 0.3 (d) 0.4
Q.17 A man walks over a rough surface,
the angle between the force of friction and the instantaneous velocity of the
person is
(a) p (b) p/2 (c) 2p (d) zero
Q.18 A lift is moving upwards with a
uniform velocity v in which a block of mass m is lying. The frictional force
offered by the block, when coefficient of friction is m, will be :
(a) zero (b) mg (c) mmg (d) 2mmg
Q.19 A body starts sliding down at an angle q to the horizontal. Then
coefficient of friction is equal to :
(a) sin q (b) cos q (c) tan q (d) cot q
Q.20 When a bicycle is in motion but
not pedaled, the force of friction exerted by the ground on the two wheels is such
that it acts :
(a)
in the backward
direction on the front wheel and in the forward direction on the rear wheel
(b)
in the forward
direction on the front wheel and in the backward direction on the rear wheel
(c)
in the forward
direction on both the wheels
(d)
in the backward
direction on both the wheels
Q.21 Pulling
force making an angle q to the horizontal is
applied on a block of weight W place on a horizontal table. If the angel of
friction is f, the magnitude of
force required to move the body is equal to :
(a) W cos f / cos (q -f) (b) W sin f / cos (q -f)
(c) W tan f / sin (q -f) (d) W sin f / tan (q -f)
Q.22 In
the case of pulling a cart, the force that causes the horse to move forward is
that force :
(a) the horse
exerts on the ground (b) the horse exerts on the cart
(c) the
ground exerts on the horse (d) the
cart exerts on the horse
ANSWER
Friction
1.
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(c)
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2.
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(a)
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3.
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(a)
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4.
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(b)
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5.
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(c)
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6.
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(b)
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7.
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(c)
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8.
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(c)
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9.
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(d)
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10.
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(c)
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11.
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(b)
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12.
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(c)
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13.
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(a)
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14.
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(d)
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15.
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(a)
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16.
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(b)
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17.
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(d)
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18.
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(a)
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19.
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(b)
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20.
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(c)
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21.
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(c)
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22.
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(a)
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CIRCULAR MOTION
Q.1 A car travelling at 20m/s on a
circular road of radius 100m. It is increasing in speed at the rate of 3m/s2.
Its acceleration is
(a) 3m/s2 (b) 4m/s2 (c) 5m/s2 (d) 3m/s2
Q.2 A particle P is moving in a circle of radius R with a uniform speedn. The centre of the circle is C
and AB is a diameter. The angular
velocity of P about A and C are in the ratio of
(a) 1:1 (b) 1:2 (c) 2:1 (d) 4 : 1
Q.3 The linear velocityn and the angular
velocity w are related to
each other by the following relation, where r
is the radius vector of the particle with respect to the center
(a) n = r ´ w (b) w = n ´ r (c) n = w ´ r (d) w = rn
Q.4 A particle is acted upon
by a force of constant magnitude which is always perpendicular to the velocity
of the particle. The motion of the particle takes place in a plane. It follows
that
(a) its velocity is constant (b) its acceleration is constant
(c) its kinetic energy is constant (d) it moves in a circular path
Q.5 Two cars of masses m1 and m2a
are moving along the circular path of radii r1
and r2. They take one
round in the same time. The ratio of their angular speeds w1/w2 is
(a) m1/ m2 (b) r1 / r2 (c) 1 : 1 (d) m1r1/m2r2
(a) mg + mn2/R (b) mg - mn2/R (c) mg (d) mg + mnR
Q.7 The string of a pendulum of length l is displaced through 90° from the
vertical and released. Then the minimum strength of the string in order to
withstand the tension as the pendulum passes through the mean position is
(a) mg (b) 3
mg (c) 5
mg (d) 6
mg
Q.8 A simple pendulum of length l having a bob of mass m is oscillating in a plane about a
vertical line between angular limits -f and +f. For an angular
displacement q(½q½<f), the tension
in the string and the velocity of the bob are T and n respectively,
the following relation holds good under the above conditions.
(a) T =
mg cosq (b) T cos q = mg
(c) T -
mg cosq = mv2/l (d) + mg
cos q = mv2/l
Q.9 A 1 kg stone at the end of 1m long string
is whirled in a vertical circle such that a constant speed of 4m/s is
maintained. The tension in the string is 6N when the stone is
(a) at the bottom of the circle (b) at the top of the circle
(c) half way down (d) none of these above.
Q.10 A can filled with water is revolved in a
vertical circle of radius 4m, the water does not fall down. The time period for
a revolution will be about
(a) 2s (b) 10s (c) 8s (d) 4s
Q.11 A bucket filled with water is whirled in a
vertical circle with a string attached to it. The water does not fall even when
the bucket is in inverted position at the top of its path. It is therefore,
concluded that
(a) mg is equal to mv2/R (b) mg is greater than mv2/R
(c) mg
is not greater than mv2/R (d) mg
is not less than mv2/R
Q.12 A smooth hemispherical bowl 0.30 m in
diameter, rotates with a constant angular velocity w about its
vertical axis of symmetry such that a particle of mass 0.5kg remain at rest,
relative to the bowl at a height 0.10 m above the base. The magnitude of w in radians per
seconds is
(a) 8 (b) 14 (c) 4.5 (d) 3
Q.13 A sphere of mass 100 gm is attached to
inextensible string of length 1.3m whose upper end is fixed in the ceiling. The
sphere is made to describe a horizontal circle of radius 50cm. The time period
of one revolution is
(a) 5.0s (b) 4.5s (c) 3.2s (d) 2.4s
Q.14 A coin is placed on a rotating turn table
just slips if it is placed at a distance of 4cm from the centre. If the angular
velocity of the turn - table is doubled, it will just slip at a distance of
(a) 1cm (b) 2cm (c) 4cm (d) 8cm
(a) m r2 w2 (b) m r w2 (c) m r2 w (d) m r2 w3
Q.16
The maximum tension which an inextensible
ring of mass 0.1kg/m can bear is 10N. The maximum velocity in m/s with which it
can be rotated is
(a) 10 (b) Ö10 (c) 20 (d) 15
Q.17 A car is going with a constant speed on an
over bridge of circular shape. As the car is ascending on the bridge, the normal
force on the car due to the bridge
(a) increase (b) decrease (c) remains
same (d) fluctuates
Q.18 A particle of mass m rotates in X-Y plane in a circle of radius a with a uniform angular speed w. It is viewed from a frame rotating about Z-axis with a uniform
angular speed w0. The
centrifugal force on the particle is
(a) m
w2a (b) m
w02a
(c) m (w+w0 / 2)2
a (d) mw w0a
Q.19 A person applies a constant force F on a particle of mass m and finds that the particle moves in a
circle of radius r with a uniform
speed n as seen from
the inertial frame of reference.
(a) This is not possible (b) There are other forces on particle
(d)
The resultant with other forces varies in magnitude as well
as in direction
Q.20 A particle is moving in a vertical circle of
radius a. Its speed vat its lowest point is sufficiently
great for the particle to describe complete circles. When the string is
horizontal the speed of the particle is
(a) Ö2ga (b) Öv2 + 2ga
(c) Öv2 - 2ga (d) Öv2 + ga
Q.21 A mass of 2kg is whirled in a horizontal
circle by means of a string at an initial speed of 5rpm. Keeping the radius
constant, the tension in the string is doubled. The new speed is nearly
(a) 14rpm (b) 10rpm (c) 20rpm (d) 7rpm
Q.22 A particle of mass m is moving in a circular path of constant radius r such that its centripetal acceleration
ac is varying with time t as ac = k2 rt2
where k is constant. The power delivered to the particle by the forces acting
on it is
(a) 2p k2r2t (b) mk2r2t (c) (mk4r2t5)/3 (d) zero
Q.23 A tube of length L is filled completely with an incompressible liquid of mass M and closed at both the ends. The tube
is then rotated in a horizontal plane about one of its end with a uniform
angular velocity w. The forces
acting exerted by the liquid at the other end is
(a) M w2 L/2 (b) Mw2L
(c) Mw2 L/4 (d) Mw2 L3/2
Q.24 A hollow cone is fixed with its axis
vertical and vertex down. A particle is describing circular motion in contact
with the inside surface of the cone in a horizontal plane at a height h above the vertex. If the inside
surface is frictionless, then the velocity of particle is
(a) Ögh (b) Ö2gh (c) Ögh/2 (d) Ö3gh/2
ANSWER
1.
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(c)
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2.
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(b)
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3.
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(c)
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4.
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(c), (d)
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5.
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(c)
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6.
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(a)
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7.
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(b)
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8.
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(c)
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9.
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(b)
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10.
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(d)
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11.
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(c)
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12.
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(b)
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13.
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(d)
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14.
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(a)
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15.
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(a)
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16.
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(a)
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17.
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(a)
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18.
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(b)
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19.
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(b), (c)
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20.
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(c)
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21.
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(d)
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22.
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(b)
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23.
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(a)
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24.
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(a)
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WORK,
POWER, ENERGY
Q.1 A
2kg body falls vertically and strikes and strikes the floor with a speed of
10m/s. It rebounds with a speed of 4m/s. The magnitude of impulse on the ball
during the impact is
(a) 8Ns (b) 12Ns
(c) 20Ns (d) 28Ns
Q.2 Two masses of
1kg and 4kg are moving with equal kinetic energies. The ratio of the magnitudes
of their linear momentum is
(a) 4 : 1 (b) 1 : Ö2 (c) 1 : 2 (d) 1 :
16
Q.3 A
projectile of mass m is fired with a
speed n at an angle of
45° with the
horizontal from a point P and reaches
Q in the same horizontal plane.
Neglecting air resistance, the magnitude of change in momentum between its
leaving P and arriving at Q is
(a) zero (b) ½ mv (c) mvÖ2 (d) 2mv
Q.4 A
radioactive nucleus initially at rest decays by emitting an electron and
neutron at right angles to each other. The momentum of the electron is 3.2 ´ 10-23 kg
ms-1 and that of neutron is 6.4 ´10-23 kg ms-1. The direction of recoiling
nucleus with that of electron motion is
(a) tan-1(0.5) (b) tan-2(2) (c) p-tan-1(2) (d) p+tan-1(2)
Q.5 A
body of mass 1 kg initially at rest, explodes and breaks into three fragment of
masses in the ratio of 1:1:3. The two pieces of equal mass fly off
perpendicular to each other, with a speed of 30m/s each. What is the velocity
of the heavier fragment?
(a) 10m/s (b) 20m/s (c) 10Ö2m/s (d) 30Ö2m/s
Q.6 Two
trains X and Y are running parallel to each other in the same direction on
frictionless rails. The train X is faster than the train B. Now, if as a consequence of exchange of packets of equal masses
between them, the acceleration of train X is a1 and that of train Y
is a2, then
(a) a1 is-ive, a2is+ive (b) a1 is+ive, a2is-ive
(c) a1=0, a2 is +ive (d) a2=0, a1 is +ive
Q.7 A
ball hits the floor and rebounds after inelastic collision. In this case
(a) the momentum of the ball just after the
collision is the same as that just before
the collision.
(b) the mechanical energy of the ball
remains the same in the collision.
(c) the total momentum of the ball and the
earth is conserved
(d) the total energy of the ball and the
earth is conserved.
Q.8 The
bob of a simple pendulum of mass m
and length l is dropped from is
horizontal position. As a consequences it strikes elastically a block of the
same mass placed on the horizontal frictionless table. The kinetic energy of
the block after collision will be
(a) 2mgl (b) mgl (c) ½ mgl (d) 0
Q.9 A ball is
dropped from a height h on the
ground. If the coefficient of restitution is e, the height to which the ball goes up after it rebounds for nth time is
(a) he2n (b) hen (c) h/en (d) h/e2n
Q.10 A
ball hits a fixed surface with a velocity u
at an angle a with the normal
to the surface at the point of impact and rebounds from it an angle b with the normal
to the surface. If the coefficient of restitution for the impact is e, then
(a) b = a (b) b
(c) tanb=e tan a (d) tanb=1/e tan a
Q.11 The head of a hammer weight 1.5kg. It falls
from a height of 0.8 m and strikes a nail and drives it into a wooden block.
The duration of impact is 0.005 s and g=10m/s2. The average impact
force exerted by the hammer is
(a) 3000N (b) 1500N (c) 1200N (d) 750N
Q.12 A hammer with a 1kg head is used to derive
nails horizontally into a wooden vertical wall. A force of 900 N is required to
penetrate the wood. Each blow should force the nail 5mm into the wall. The
velocity of the hammers head when it strikes the nail is
(a) 9m/s (b) 6m/s (c) 3m/s (d) 1m/s
Q.13 A body of mass 0.5 kg moving at a speed of
4m/s colludes with another body of mass 1.0kg. After the collision the two
bodies stick together and remain motionless. The velocity of 1.0kg mass before
impact is
(a) 2m/s (b) zero (c) –2m/s (d) –4m/s
Q.14 Two bodies each of mass 1kg move towards
each other in mutually perpendicular directions with velocities 4m/s and 2m/s.
If the two bodies sticks together after collision, the heat liberated will be
(a) 4J (b) 5J (c) 6J (d) 16J
Q.15 A bomb of mass 3kg which is at rest explodes
into three fragment of equal masses. Two of the fragment are found to move with
a speed of 1m/s each in mutually perpendicular directions. The total energy
released during explosion is
(a) 1.5J (b) 2J (c) 4J (d) 5J
Q.16 A bomb of 12kg explodes into two pieces of
masses 4kg and 8kg. The velocity of 8kg mass is 6m/s. The kinetic energy of the
other mass is
(a) 48J (b) 32J (c) 24J (d) 288J
Q.17 A 50g bullet moving with velocity 10m/s
strikes a block of mass 950g at rest and gets embedded in it. The loss of
kinetic energy will be
(a) 100% (b) 95% (c) 5% (d) 50%
Q.18 Consider two particles of equal masses. One
of the particles is at rest while the other is moving with a constant
acceleration a. The center of mass of
the system of the two particles has an acceleration
(a) zero (b) ½ a (c) a (d) 2a
Q.19 Two balls of unequal masses are thrown
simultaneously in air. The acceleration of the center of mass of the two balls
while in air
(a) depends on masses of the balls
(b) depends on directions of motion of balls
(c) depends both on masses and direction of
motion
(d) is equal to Ig.
Q.20 Two particles A and B initially at
rest, move towards each other under a mutual force of attraction. At the
instant when the speed of A is v and the speed of B is 2v, the speed of the
center of mass of the system is
(a) zero (b) v
(c) 1.5v (d) 2v
Q.21 A bomb travelling
in a parabolic path under the effect of gravity explodes in mid air. The center
of mass of the fragments will continue to move
(a) along a hyperbolic path
(b) vertically
upwards and then vertically downwards
(c) horizontally in the forward direction
(d) along the original parabolic path.
Q.22 Masses of 4 kg and 12kg are approaching each
other on a frictionless surface with speeds 6m/s eastward and 10m/s westward
respectively. The velocity of the center of mass is
(a) 4m/s east (b) 6m/s west (c) 8
m/s east (d) 0
Q.23 A boat of mass 45kg is floating in still
water. A dog of mass 15kg walks from the stern to the bow. The length of the
boat is 3m. What distance does the boat move?
(a) 1.5m (b) 1.0m (c) 0.75m (d) 0.25m
Q.24 Internal forces can change
(a) linear
momentum but not kinetic energy
(b) kinetic energy but not linear momentum
(c) both linear momentum and kinetic energy
(d) neither linear momentum nor kinetic
energy
Q.25 A body is moved along a straight line by a
machine delivering a constant power. The distance travelled by the body in time
t is proportional to
(a) t1/2 (b) t3/4 (C) t3/2 (d) t2
Q.26 A uniform chain of length l and mass m is lying on a smooth table and one third of its length is hanging
vertically down over the edge of the table. If g is acceleration due to gravity, the work required to pull the
hanging part on the table is
(a) mgl
(b) 1/3 mgl
(c) 1/9 mgl (d) 1/18
mgl
Q.27 A lift pump works normally at 200V, 10A. It
pumps water to an average height of 15m to fill a tank of volume 3m´2m´1m. If the
efficiency of the pump is 75%, the time in minute required to fill the tank is
nearly
(a) 5 (b) 10 (c) 20 (d) 120
Q.28 If g
is the acceleration due to gravity on the earth’s surface, the gain in
potential energy of an object of mass m
raised from the surface of the earth to a height equal to radius R of the earth is
(a) mg
R/2 (b) 2
mg R (c) mg
R (d) ¼ mg
R
Q.29 When the mass of 20g is hanged to one end of
a light spring of length 10cm, the spring is stretched by 2cm. The mass is
pulled down until the total length of the spring is 14cm. The elastic energy in
J, stored in the spring is
(a) 8 ´ 10-2 (b) 4 ´ 10-2 (c) 2 ´ 10-3 (d) 8 ´ 10-3
Q.30 A block of mass 1kg is permanently attached
with a spring of spring constant k=100N/m.
The spring is compressed 0.20m and placed on a horizontal smooth surface. When
the block is released, it moves to a point 0-4m beyond the point when the
spring is at its natural length. The work done by the spring in changing from
compressed state to the stretched state is
(a) 10J (b) –6J (c) –8J (d) 18J
ANSWER SHEET
1.
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(d)
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2.
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(c)
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3.
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(c)
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4.
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(d)
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5.
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(c)
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6.
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(a)
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7.
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(c)
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8.
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(b)
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9.
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(a)
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10.
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(d)
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11.
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(c)
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12.
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(c)
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13.
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(c)
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14.
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(b)
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15.
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(b)
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16.
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(d)
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17.
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(b)
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18.
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(b)
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19
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(d)
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20.
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(a)
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21.
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(d)
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22.
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(b)
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23.
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(c)
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24.
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(b)
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25.
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(c)
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26.
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(d)
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27.
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(b)
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28.
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(a)
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29.
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(d)
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30.
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(b)
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Please send explanations.
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