Laws of Motion- 3 Practice Questions - DPP for NEET

 Page 1


DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A body of mass 400 g slides on a rough horizontal surface.
If the frictional force is 3.0 N, the angle made by the contact
force on the body with the vertical will be
(a) 37º (b) 53º (c) 63º (d) 27º
Q.2 In the above question, the magnitude of the contact force
is
(g = 10 m/s
2
)
(a) 3.0 N (b) 4.0 N (c) 5.0 N (d) 7.0 N
Q.3 The coefficient of static friction between a block of mass
m and an inclined plane is m
s
 = 0.3. What can be the
maximum angle q of the inclined plane with the horizontal
so that the block does not slip on the plane?
(a) tan
–1
 (0.1) (b) tan
–1
 (0.2)
(c) tan
–1
 (0.3) (d) tan
–1
 (0.4)
Q.4 The coefficient of static friction between the two blocks
shown in figure is m and the table is smooth. What maximum
horizontal force F can be applied to the block of mass M
so that the blocks move together?
F M
m
(a) mg (M + m) (b) mg (M – m)
(c)2mg (M + m) (d) mg (M + 2m)
Page 2


DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A body of mass 400 g slides on a rough horizontal surface.
If the frictional force is 3.0 N, the angle made by the contact
force on the body with the vertical will be
(a) 37º (b) 53º (c) 63º (d) 27º
Q.2 In the above question, the magnitude of the contact force
is
(g = 10 m/s
2
)
(a) 3.0 N (b) 4.0 N (c) 5.0 N (d) 7.0 N
Q.3 The coefficient of static friction between a block of mass
m and an inclined plane is m
s
 = 0.3. What can be the
maximum angle q of the inclined plane with the horizontal
so that the block does not slip on the plane?
(a) tan
–1
 (0.1) (b) tan
–1
 (0.2)
(c) tan
–1
 (0.3) (d) tan
–1
 (0.4)
Q.4 The coefficient of static friction between the two blocks
shown in figure is m and the table is smooth. What maximum
horizontal force F can be applied to the block of mass M
so that the blocks move together?
F M
m
(a) mg (M + m) (b) mg (M – m)
(c)2mg (M + m) (d) mg (M + 2m)
2
DPP/ P 11
Q.5 Block A weighs 4 N and block B weighs 8 N. The coef ficient of
kinetic friction is 0.25 fo r all surfaces. Find the f orce F to slide B at
a constant speed when A rests on B and moves with it.
(a) 2N (b) 3N (c) 1N (d) 5N
Q.6 In the above question, find the force F to slide B at a
constant speed when A is held at rest.
(a) 2N (b) 3N (c) 1N (d) 4N
Q.7 In the above question, find the force F to slide B at a
constant speed when A and B are connected by a light cord
passing over a smooth Pulley.
(a) 2N (b) 3N (c) 1N (d) 5N
Q.8 Find the maximum value of M/m in the situation shown in
figure so that the system remains at rest. Friction
coefficient at both the contacts is m.
M
m
q
(a)
sin cos
m
q-mq
(b)
2
sin cos
m
q-mq
(c)
sin cos
m
q+mq
(d)
cos sin
m
q-mq
Q.9 A block placed on a horizontal surface is being pushed by
a force F making an angle q with the vertical, if the
coefficient of friction is m, how much force is needed to
get the block just started?
(a)
sin cos
m
q-mq
(b)
2
sin cos
m
q-mq
(c)
sin cos
m
q+mq
(d)
cos sin
m
q-mq
Q.10 Assuming the length of a chain to be L and coefficient of
static friction m. Compute the maximum length of the chain
which can be held outside a table without sliding.
(a)
2L
1
m
+m
(b)
L
1
m
-m
(c)
L
1
m
+m
(d)
3L
1
m
+m
Q.11 If the coefficient of friction between an insect and bowl is
m and the radius of the bowl is r, find the maximum height
to which the insect can crawl in the bowl.
(a) R
2
1
1
( 1)
éù
êú
+
êú
m+
ëû
(b) R
2
1
1
( 1)
éù
êú
-
êú
m-
ëû
(c)R
2
2
1
( 1)
éù
êú
-
êú
m+
ëû
(d) R
ú
ú
û
ù
ê
ê
ë
é
+ m
-
) 1 (
1
1
2
Q.12A body of mass m is released from the top of a rough
inclined plane as shown in figure. If the frictional force be
F, then body will reach the bottom with a velocity
L
h
m
(a)
2
(mgh FL)
m
- (b)
1
(mgh FL)
m
-
(c)
2
(mgh FL)
m
+ (d) None of these
Q.13 A block of mass 2 kg is placed on the floor. The coefficient
of static friction is 0.4.A force F of 2.5 N is applied on the
block, as shown. Calculate the force of friction between
the block and the floor. (g = 9.8 ms
–2
)
(a) 2.5 N (b) 25 N (c) 7.84 N (d) zero
Q.14 A block is kept on a horizontal table. The table is undergoing
simple harmonic motion of frequency 3 Hz in a horizontal
plane. The coefficient of static friction between the block and
the table surface is 0.72. Find the maximum amplitude of the
table at which the block does not slip on the surface  (g = 10 ms
–
2
)
(a) 0.01 m (b) 0.02 m (c) 0.03 m (d) 0.04 m
Q.15 Two cars of unequal masses use similar tyres. If they are
moving at the same initial speed, the minimum stopping
distance -
(a) is smaller for the heavier car
(b) is smaller for the lighter car
(c) is same for both cars
(d) depends on the volume of the car
Page 3


DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A body of mass 400 g slides on a rough horizontal surface.
If the frictional force is 3.0 N, the angle made by the contact
force on the body with the vertical will be
(a) 37º (b) 53º (c) 63º (d) 27º
Q.2 In the above question, the magnitude of the contact force
is
(g = 10 m/s
2
)
(a) 3.0 N (b) 4.0 N (c) 5.0 N (d) 7.0 N
Q.3 The coefficient of static friction between a block of mass
m and an inclined plane is m
s
 = 0.3. What can be the
maximum angle q of the inclined plane with the horizontal
so that the block does not slip on the plane?
(a) tan
–1
 (0.1) (b) tan
–1
 (0.2)
(c) tan
–1
 (0.3) (d) tan
–1
 (0.4)
Q.4 The coefficient of static friction between the two blocks
shown in figure is m and the table is smooth. What maximum
horizontal force F can be applied to the block of mass M
so that the blocks move together?
F M
m
(a) mg (M + m) (b) mg (M – m)
(c)2mg (M + m) (d) mg (M + 2m)
2
DPP/ P 11
Q.5 Block A weighs 4 N and block B weighs 8 N. The coef ficient of
kinetic friction is 0.25 fo r all surfaces. Find the f orce F to slide B at
a constant speed when A rests on B and moves with it.
(a) 2N (b) 3N (c) 1N (d) 5N
Q.6 In the above question, find the force F to slide B at a
constant speed when A is held at rest.
(a) 2N (b) 3N (c) 1N (d) 4N
Q.7 In the above question, find the force F to slide B at a
constant speed when A and B are connected by a light cord
passing over a smooth Pulley.
(a) 2N (b) 3N (c) 1N (d) 5N
Q.8 Find the maximum value of M/m in the situation shown in
figure so that the system remains at rest. Friction
coefficient at both the contacts is m.
M
m
q
(a)
sin cos
m
q-mq
(b)
2
sin cos
m
q-mq
(c)
sin cos
m
q+mq
(d)
cos sin
m
q-mq
Q.9 A block placed on a horizontal surface is being pushed by
a force F making an angle q with the vertical, if the
coefficient of friction is m, how much force is needed to
get the block just started?
(a)
sin cos
m
q-mq
(b)
2
sin cos
m
q-mq
(c)
sin cos
m
q+mq
(d)
cos sin
m
q-mq
Q.10 Assuming the length of a chain to be L and coefficient of
static friction m. Compute the maximum length of the chain
which can be held outside a table without sliding.
(a)
2L
1
m
+m
(b)
L
1
m
-m
(c)
L
1
m
+m
(d)
3L
1
m
+m
Q.11 If the coefficient of friction between an insect and bowl is
m and the radius of the bowl is r, find the maximum height
to which the insect can crawl in the bowl.
(a) R
2
1
1
( 1)
éù
êú
+
êú
m+
ëû
(b) R
2
1
1
( 1)
éù
êú
-
êú
m-
ëû
(c)R
2
2
1
( 1)
éù
êú
-
êú
m+
ëû
(d) R
ú
ú
û
ù
ê
ê
ë
é
+ m
-
) 1 (
1
1
2
Q.12A body of mass m is released from the top of a rough
inclined plane as shown in figure. If the frictional force be
F, then body will reach the bottom with a velocity
L
h
m
(a)
2
(mgh FL)
m
- (b)
1
(mgh FL)
m
-
(c)
2
(mgh FL)
m
+ (d) None of these
Q.13 A block of mass 2 kg is placed on the floor. The coefficient
of static friction is 0.4.A force F of 2.5 N is applied on the
block, as shown. Calculate the force of friction between
the block and the floor. (g = 9.8 ms
–2
)
(a) 2.5 N (b) 25 N (c) 7.84 N (d) zero
Q.14 A block is kept on a horizontal table. The table is undergoing
simple harmonic motion of frequency 3 Hz in a horizontal
plane. The coefficient of static friction between the block and
the table surface is 0.72. Find the maximum amplitude of the
table at which the block does not slip on the surface  (g = 10 ms
–
2
)
(a) 0.01 m (b) 0.02 m (c) 0.03 m (d) 0.04 m
Q.15 Two cars of unequal masses use similar tyres. If they are
moving at the same initial speed, the minimum stopping
distance -
(a) is smaller for the heavier car
(b) is smaller for the lighter car
(c) is same for both cars
(d) depends on the volume of the car
DPP/ P 11
3
Q.16 Consider the situation shown in figure. The wall is smooth
but the surfaces of A and B in contact are rough in
equilibrium the friction on B due to A –
(a) is upward
(b) is downward                                                
B A F
(c) is zero
(d) the system cannot remain in equilibrium
Q.17 A block is placed on a rough floor and a horizontal  force F
is applied on it. The force of friction f by the floor on the
block is measured for different values of F and a graph is
plotted between them –
(i) The graph is a straight line of slope 45°
(ii) The graph is straight line parallel to the F axis
(iii) The graph is a straight line of slope 45º for small F and
a straight line parallel to the F-axis for large F.
(iv) There is small kink on the graph
(a) iii, iv (b) i, iv (c) i, ii (d) i, iii
Q.18 The contact force exerted by a body A on another body B
is equal to the normal force between the bodies. We
conclude that -
(i) the surfaces must be smooth
(ii) force of friction between two bodies may be equal to
zero
(iii) magnitude of normal reaction is equal to that of
friction
(iv) bodies may be rough
(a) ii, iv (b) i, ii (c) iii, iv (d) i, iv
Q.19 It is easier to pull a body than to push, because -
(a) the coefficient of friction is more in pushing than that
in pulling
(b) the friction force is more in pushing than that in
pulling
(c) the body does not move forward when pushed
(d) None of these
Q.20A block of metal is lying on the floor of a bus. The
maximum acceleration which can be given to the bus so
that the block may remain at rest, will be -
(a) µg (b) µ/g (c)µ
2
g (d) µg
2
DIRECTIONS (Q.21-Q.23) : In the following questions, more
than one of the answers  given are correct. Select the correct
answers and mark it according to the following codes:
Codes :
(a) 1, 2 and 3 are correct (b) 1 and 2 are correct
(c) 2 and 4 are correct (d) 1 and 3 are correct
Q.21Choose the correct statements –
(1) Kinetic friction is lesser than limiting friction.
(2) In rolling the surfaces at contact do not rub each other.
(3) If a body is at rest and no pulling force is acting on it,
force of friction on it is zero.
(4) Kinetic friction is greater than limiting friction.
Q.22Choose the correct statements –
(1) Force of friction is partically independent of
microscopic area of surface in contact and relative
velocity between them. (if it is not high)
(2) Normally with increase in smoothness friction
decreases. But if the surface area are made too smooth
by polishing and cleaning the bonding force of
adhesion will increase and so the friction will increase
resulting in 'Cold welding'
(3) Friction is a non conservative force, i.e. work done
against friction is path dependent.
(4) Force of fricton depends on area
Q.23Choose the correct options –
(1) Friction always opposes the motion
(2) Friction may opposes the motion
(3) If the applied force is increased the force of static
friction remains constant.
(4) If the applied force is increased the force of static
friction also increases upto limiting friction.
DIRECTIONS (Q.24-Q.26) : Read the passage given below and
answer the questions that follows :
A block of mass 1 kg is placed on a rough horizontal surface. A
spring is attached to the block whose other end is joined to a rigid
wall, as shown in the figure. A horizontal force is applied on the
block so that it remains at rest while the spring is elongated by x.
Page 4


DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A body of mass 400 g slides on a rough horizontal surface.
If the frictional force is 3.0 N, the angle made by the contact
force on the body with the vertical will be
(a) 37º (b) 53º (c) 63º (d) 27º
Q.2 In the above question, the magnitude of the contact force
is
(g = 10 m/s
2
)
(a) 3.0 N (b) 4.0 N (c) 5.0 N (d) 7.0 N
Q.3 The coefficient of static friction between a block of mass
m and an inclined plane is m
s
 = 0.3. What can be the
maximum angle q of the inclined plane with the horizontal
so that the block does not slip on the plane?
(a) tan
–1
 (0.1) (b) tan
–1
 (0.2)
(c) tan
–1
 (0.3) (d) tan
–1
 (0.4)
Q.4 The coefficient of static friction between the two blocks
shown in figure is m and the table is smooth. What maximum
horizontal force F can be applied to the block of mass M
so that the blocks move together?
F M
m
(a) mg (M + m) (b) mg (M – m)
(c)2mg (M + m) (d) mg (M + 2m)
2
DPP/ P 11
Q.5 Block A weighs 4 N and block B weighs 8 N. The coef ficient of
kinetic friction is 0.25 fo r all surfaces. Find the f orce F to slide B at
a constant speed when A rests on B and moves with it.
(a) 2N (b) 3N (c) 1N (d) 5N
Q.6 In the above question, find the force F to slide B at a
constant speed when A is held at rest.
(a) 2N (b) 3N (c) 1N (d) 4N
Q.7 In the above question, find the force F to slide B at a
constant speed when A and B are connected by a light cord
passing over a smooth Pulley.
(a) 2N (b) 3N (c) 1N (d) 5N
Q.8 Find the maximum value of M/m in the situation shown in
figure so that the system remains at rest. Friction
coefficient at both the contacts is m.
M
m
q
(a)
sin cos
m
q-mq
(b)
2
sin cos
m
q-mq
(c)
sin cos
m
q+mq
(d)
cos sin
m
q-mq
Q.9 A block placed on a horizontal surface is being pushed by
a force F making an angle q with the vertical, if the
coefficient of friction is m, how much force is needed to
get the block just started?
(a)
sin cos
m
q-mq
(b)
2
sin cos
m
q-mq
(c)
sin cos
m
q+mq
(d)
cos sin
m
q-mq
Q.10 Assuming the length of a chain to be L and coefficient of
static friction m. Compute the maximum length of the chain
which can be held outside a table without sliding.
(a)
2L
1
m
+m
(b)
L
1
m
-m
(c)
L
1
m
+m
(d)
3L
1
m
+m
Q.11 If the coefficient of friction between an insect and bowl is
m and the radius of the bowl is r, find the maximum height
to which the insect can crawl in the bowl.
(a) R
2
1
1
( 1)
éù
êú
+
êú
m+
ëû
(b) R
2
1
1
( 1)
éù
êú
-
êú
m-
ëû
(c)R
2
2
1
( 1)
éù
êú
-
êú
m+
ëû
(d) R
ú
ú
û
ù
ê
ê
ë
é
+ m
-
) 1 (
1
1
2
Q.12A body of mass m is released from the top of a rough
inclined plane as shown in figure. If the frictional force be
F, then body will reach the bottom with a velocity
L
h
m
(a)
2
(mgh FL)
m
- (b)
1
(mgh FL)
m
-
(c)
2
(mgh FL)
m
+ (d) None of these
Q.13 A block of mass 2 kg is placed on the floor. The coefficient
of static friction is 0.4.A force F of 2.5 N is applied on the
block, as shown. Calculate the force of friction between
the block and the floor. (g = 9.8 ms
–2
)
(a) 2.5 N (b) 25 N (c) 7.84 N (d) zero
Q.14 A block is kept on a horizontal table. The table is undergoing
simple harmonic motion of frequency 3 Hz in a horizontal
plane. The coefficient of static friction between the block and
the table surface is 0.72. Find the maximum amplitude of the
table at which the block does not slip on the surface  (g = 10 ms
–
2
)
(a) 0.01 m (b) 0.02 m (c) 0.03 m (d) 0.04 m
Q.15 Two cars of unequal masses use similar tyres. If they are
moving at the same initial speed, the minimum stopping
distance -
(a) is smaller for the heavier car
(b) is smaller for the lighter car
(c) is same for both cars
(d) depends on the volume of the car
DPP/ P 11
3
Q.16 Consider the situation shown in figure. The wall is smooth
but the surfaces of A and B in contact are rough in
equilibrium the friction on B due to A –
(a) is upward
(b) is downward                                                
B A F
(c) is zero
(d) the system cannot remain in equilibrium
Q.17 A block is placed on a rough floor and a horizontal  force F
is applied on it. The force of friction f by the floor on the
block is measured for different values of F and a graph is
plotted between them –
(i) The graph is a straight line of slope 45°
(ii) The graph is straight line parallel to the F axis
(iii) The graph is a straight line of slope 45º for small F and
a straight line parallel to the F-axis for large F.
(iv) There is small kink on the graph
(a) iii, iv (b) i, iv (c) i, ii (d) i, iii
Q.18 The contact force exerted by a body A on another body B
is equal to the normal force between the bodies. We
conclude that -
(i) the surfaces must be smooth
(ii) force of friction between two bodies may be equal to
zero
(iii) magnitude of normal reaction is equal to that of
friction
(iv) bodies may be rough
(a) ii, iv (b) i, ii (c) iii, iv (d) i, iv
Q.19 It is easier to pull a body than to push, because -
(a) the coefficient of friction is more in pushing than that
in pulling
(b) the friction force is more in pushing than that in
pulling
(c) the body does not move forward when pushed
(d) None of these
Q.20A block of metal is lying on the floor of a bus. The
maximum acceleration which can be given to the bus so
that the block may remain at rest, will be -
(a) µg (b) µ/g (c)µ
2
g (d) µg
2
DIRECTIONS (Q.21-Q.23) : In the following questions, more
than one of the answers  given are correct. Select the correct
answers and mark it according to the following codes:
Codes :
(a) 1, 2 and 3 are correct (b) 1 and 2 are correct
(c) 2 and 4 are correct (d) 1 and 3 are correct
Q.21Choose the correct statements –
(1) Kinetic friction is lesser than limiting friction.
(2) In rolling the surfaces at contact do not rub each other.
(3) If a body is at rest and no pulling force is acting on it,
force of friction on it is zero.
(4) Kinetic friction is greater than limiting friction.
Q.22Choose the correct statements –
(1) Force of friction is partically independent of
microscopic area of surface in contact and relative
velocity between them. (if it is not high)
(2) Normally with increase in smoothness friction
decreases. But if the surface area are made too smooth
by polishing and cleaning the bonding force of
adhesion will increase and so the friction will increase
resulting in 'Cold welding'
(3) Friction is a non conservative force, i.e. work done
against friction is path dependent.
(4) Force of fricton depends on area
Q.23Choose the correct options –
(1) Friction always opposes the motion
(2) Friction may opposes the motion
(3) If the applied force is increased the force of static
friction remains constant.
(4) If the applied force is increased the force of static
friction also increases upto limiting friction.
DIRECTIONS (Q.24-Q.26) : Read the passage given below and
answer the questions that follows :
A block of mass 1 kg is placed on a rough horizontal surface. A
spring is attached to the block whose other end is joined to a rigid
wall, as shown in the figure. A horizontal force is applied on the
block so that it remains at rest while the spring is elongated by x.
4
DPP/ P 11
mg
x
k
m
³ . Let F
max
 and F
min
 be the maximum and minimum values
of force F for which the block remains a equilibrium. For a particular
x,
F
max
 – F
min
 = 2N.
Also shown is the variation of F
max
 + F
min
 versus x, the elonga-
tion of the spring.
//////////////////////////////////////////
///////////////
1 kg
K
 
5N
F +F
max min
x
0.1M
Q.24 The coefficient of friction between the block and the hori-
zontal surface is –
(a) 0.1 (b) 0.2
(c) 0.3 (d) 0.4
Q.25 The spring constant of the spring is –
(a) 25 N/m (b) 20 N/m
(c) 2.5 N/m (d) 50 N/m
Q.26 The value of F
min
, if x = 3 cm. is –
(a)0 (b) 0.2 N
(c) 5N (d) 1N
DIRECTIONS (Q. 27-Q.28) : Each of these questions contains
two statements: Statement-1 (Assertion) and Statement-2
(Reason). Each of these questions has four alternative choices, only
one of which is the correct answer . Y ou have to select the correct
choice.
(a) Statement-1 is True, Statement-2 is True; Statement-2 is a
correct explanation for  Statement-1.
(b) Statement-1 is True, Statement-2 is True; Statement-2 is
NOT a correct explanation for Statement-1.
(c) Statement -1 is False, Statement-2 is True.
(d) Statement -1 is True, Statement-2 is False.
Q.27 A solid sphere and a hollow sphere of same mass M and
same radius R are released from the top of a rough
inclined plane. Friction coefficient is same for both the
bodies. If both bodies perform imperfect rolling, then
Statement - 1 : Work done by friction for the motion of
bodies from top of incline to the bottom will be same
for both the bodies.
Statement - 2 :  Force of friction will be same for both
the bodies.
Q.28 Statement - 1 : Maximum value of friction force between
two surfaces is m
  
× normal reaction.
where m = coefficient of friction between surfaces.
Statement - 2  : Friction force between surfaces of two
bodies is always less than or equal to externally applied
force.