Questions from dynamics

1. According to the third law of motion, action

and reaction
A. Always act on the same body
B. Always cancel each other
C. Always act on two different bodies in opposite
directions
D. Have the same magnitude and directions
2.Three blocks of masses 2kg, 3kg and 5kg are
connected to each other with light string and
are then placed on a frictionless surface as
shown in the figure. The system is pulled by a
force F = 10N, then T2 is:

A.3N B. 4N
C. 5N D. 6N
3.A block A of mass 4kg is placed on a
frictionless table. A thread tied to it passes over
a frictionless pulley and carries a body B of mass
6 kg at the other end. The acceleration of the
system is: A. 6 m/s2
B. 10m/s2
C. 4 m/s2
D. 12 m/s2
4.A 2-kg block slides down a 30° incline as
shown below with an acceleration of 2m/s2 .
Which of the following correctly indicates the
value of coefficient of friction b/n the surface
and the block?
.
.
A. 0.2 C. 0.7
B. 0.6 D.0.4
5.A particle is subject to a force that varies with
position as shown in Figure below. What is the
amount work done by the force on the particle
as it moves from x= 0 to x= 12m?

. .
A. 21J
B. 24J .
..
C. 18J
D.22J
6.A ring (I=MR2) is released and rolled down an
inclined plane which is 10m above the horizontal
ground. what is the linear velocity of the ring at
the bottom of the incline?
7. Which of the following statements is false for
collisions?
A. Momentum is conserved in elastic collisions
but not in inelastic collisions.
B. Total kinetic energy is not conserved in
inelastic collisions but momentum is conserved
C. Total-kinetic energy is conserved in elastic
collisions but momentum is not conserved.
D. Total kinetic energy and momentum both are
conserved in all types of collisions
8.Which of the following is incorrect about
frictional force?
A. static friction is greater than kinetic friction
force.
B. we can avoid friction force by lubricating
between two surfaces.
C. frictional force is proportional to normal
force.
D. friction force is the most important in our
daily life.
9.Three boxes are connected with massless light
ropes and a horizontal pulling force F is exerted
on the box of mass M1 as shown in the figure
below. If the coefficient of kinetic friction
between each of the boxes and the horizontal
floor is µ, which one is correct expression to
calculate the acceleration of the system?
10.Which of the following best describes the
relationship between weight and normal force
for an object resting on a horizontal surface, if
an external force F is acting as shown below?
A. Weight is greater than the normal force
B. Weight is equal to the normal force
C. Weight is less than the normal force
D. Weight is independent of the normal force.
11. A box that weights 60N is on a ramp, which
is inclined at 30° to the horizontal as shown in
figure below. The box is in limiting equilibrium.
What is the coefficient of friction between the
box and the plane?
A. 0.73 B. 0.58. C.0.63 D. 0.43.
12. Newton’s first law means a force is always required to make
an object:
A. Remains at rest.
C. Speed up or speed down.
B. Moves in uniform motion.
D. A and B
13. Which one of the following statements is true about action
and reaction forces referred to in Newton’s third law of motion?
A. They act up on the same body.
B. They are equal in magnitude and have the same direction.
C. They act up on two different bodies.
D. They are not equal in magnitude but have the same line of
action.
14. . A man is standing on a spring scale in an
elevator. When the elevator is at rest, the scale
reads 560N. When the elevator starts to move,
the scale reads 500N. The elevator has:
A. An upward acceleration.
B. A constant upward speed.
C. A constant downward speed.
D. Downward acceleration
15. A ball of mass m1=2kg and a block of mass
m2=6kg are attached by a lightweight cord that
passes over a frictionless pulley of negligible
mass, as shown in the figure below. The block
lies on a frictionless incline of angle θ=370 .What
is the magnitude of the acceleration of the two
objects?
A. 6m/s2
B. 2m/s2
C. 4m/s2
D. 8m/s2
16. A block of mass m 20 kg is pulled up at ɵ =37°
incline as in Figure shown below with a force of
magnitude F =100 N.
(a) Find the acceleration of the block if the incline is
frictionless.
(b) Find the acceleration of the block if the coefficient
of kinetic friction between the block and incline is 0.10.
17. A 2kg aluminum block and a 6kg copper
block are connected by a light string over a
frictionless pulley. The two blocks are allowed to
move on a fixed steel block wedge (of angle ɵ=
30°) as shown in Figure below. determine (a) the
acceleration of the two blocks and (b) the
tension in the string.
18. A 50kg circus acrobat
drops from a height of 2m
straight down onto
a springboard
with a force constant of
8x103 N/m,
as shown in Figure below.
By what maximum
distance does she
compress the spring?
19. A 5.0-kg block is pushed 3.0 m up a vertical wall
with constant speed by a constant force of magnitude F
applied at an angle of ɵ= 30° with the horizontal, as
shown in Figure below. If the coefficient of kinetic
friction between block and wall is 0.30, determine the
work done by
(a) F , (b) the force of gravity, and
(c) the normal force between block
and wall.(d) By how much does the
gravitational potential energy
increase during the block’s motion?
20. . Which of the following describes the work-
energy principle?
A) Work and energy are unrelated.
B) Energy cannot be created but can be
destroyed.
C) Work done is equal to the change in kinetic
energy.
D) Work is done only when an object moves.
21. Which of the following factors affects the
magnitude of the force of friction between two
surfaces?
A) The normal force pressing the two surfaces
together.
B) The surface area of contact between the two
surfaces.
C) The relative velocity between the two
surfaces.
D) The temperature of the surfaces.
22. A block of mass 10 kg is suspended by two
ropes as shown in the diagram. What is the
tension in rope 1 (T1)?
A) 40 N
B) 60 N
C) 80 N
D) 100 N
23. . Which of the following statements BEST distinguishes
between conservative and non -conservative forces?
A) Work done by a conservative force along any closed
path is zero, whereas the work done by non-
conservative force along a closed path is not zero.
B) B) Work done by conservative force is path dependent,
whereas work done by non-conservative force does
not depend on the path followed.
C) C) Friction force is an example of conservative force,
whereas spring force and gravitational forces are
examples of non-conservative forces.
D) D) A conservative force dissipates energy, whereas a
non-conservative force does not.
24. A pendulum is released from a height of 5 m
above its lowest point. At what point in the
swing will the pendulum have its maximum
kinetic energy?
A) At the highest point on either side
B) B) Halfway down
C) C) At the lowest point
D) D) At three-quarters of the way down
25. The apparent weight of a 60kg student
standing inside a lift is
A. 600N when the lift accelerates with
acceleration equal to gravitational.
B. 720N when the lift is at rest.
C. 600N when the lift accelerates upward with
2m/s2.
D. 480N when the lift accelerates downward
with 2m/s2.
26.Two balls have equal masses and the
coefficient of friction is 0.2,what is the
acceleration of the blocks?
27.A block of 5kg is released from point A .the
track is friction less except portion BC of length
2m. The block moves down the track and hits a
spring of K=2000N/m and compress it 0.2m from
its rest position. what is ;
A.The friction force on portion BC?
B. The coefficient of friction b/n surface BC and
the block?
28.A horizontal force 100N is used to hold a
block stationary against a wall. The coefficient of
friction b/n the block and the wall is 0.2 .what is
the mass the bock?

F=100N
29. A 1 kg ball is released from the top of an 1.8
m high tower. Neglecting air resistance,
Calculate
A. The height of the ball above the ground when
its kinetic energy is half of its potential energy.
B. The speed of the ball when its kinetic energy
is three times its potential energy.
C.The potential energy at a point where v=5m/s.
30..A force of F =(2i + 4j)N is exerted on a block
to move it with a velocity of v=(6j+8k )m/s. what
is the power exerted on the block?