PHY for ENG 2

Question 1

Two objects move toward each other,
collide, and separate. If there was no net external force acting on the objects, but some kinetic energy was lost, then:

A. the collision was elastic and total linear
momentum was not conserved
B. the collision was not elastic and total
linear momentum was not conserved
C. the collision was elastic and total linear
momentum was conserved
D. the collision was not elastic and total
linear momentum was conserved

Answer 1

D. the collision was not elastic and total
linear momentum was conserved

Total linear momentum is conserved in a collision during which the net external force is zero. If kinetic energy is lost,
then by definition, the collision is not
elastic.

Question 2

When a body moves with a constant
speed along a circle

A. no work is done on it
B. no acceleration is produced in it
C. no force acts on it
D. its velocity remains constant

Answer 2

A. no work is done on it

Question 3

The coefficient of restitution e for a
perfectly elastic collision is:

A. -1
B. 0
C. 1
D. Infinity

Answer 3

C. 1

Question 4

A drum of radius R and mass M, rolls
down without slipping along an inclined
plane of angle 0. The frictional force:

A. Decreases the rotational motion
B. Decreases the rotational and translational
motion
C. Dissipates energy as heat
D. Converts translational energy to
rotational energy

Answer 4

D. Converts translational energy to
rotational energy

Solution: Net work done by frictional force when drum
rolls down without slipping is zero.
Wre=0

(P4Eng2 FIGURE)

Question 5

A wooden block of mass M is moving at
speed V in a straight line. How fast
would the bullet of mass m need to
travel to stop the block (assuming that
the bullet became embedded inside)?

A. MV/m
B. mV/(m+M)
C. mV/M
D. MV/(m+M)

Answer 5

A. MV/m

(P4Eng2 FIGURE)

Question 6

Which of the following best describes a
perfectly inelastic collision free of
external forces?

A. Kinetic energy is sometimes conserved
B. Total linear momentum is never
conserved
C. Total linear momentum is sometimes
conserved.
D. Kinetic energy is never conserved.

Answer 6

D. Kinetic energy is never conserved.

In a perfectly inelastic collision, kinetic energy is never conserved; some of the initial kinetic energy is always lost to
heat and some is converted to potential
energy in the deformed shapes of the
objects as they lock together.

Question 7

A solid cylinder of mass m and radius R rolls down an inclined plane of height h without slipping. The speed of its centre of mass when it reaches the bottom is:

A. √(4gh/3)
B. √(4g/h)
C. √(2gh)
D. √(3gh/4)

Answer 7

A. √(4gh/3)

Question 8

The vector sum of two forces is
perpendicular to their vector
differences. In that case, the forces

A. are equal to each other
B. are equal to each other in magnitude
C. cannot be predicted
D. are not equal to each other in magnitude

Answer 8

B. are equal to each other in magnitude

Question 9

A particle of mass m is projected with velocity v making an angle of 45° with the horizontal. When the particle lands on the level ground the magnitude of the change in its momentum will be:

A. 2mv
B. zero
C. mv√(2)
D. mv/√(2)

Answer 9

C. mv√(2)

Question 10

For a satellite moving in an orbit around the earth, the ratio of kinetic energy to potential energy is:

A. 1/2
B. 1/√(2)
C. 2
D. √(2)

Answer 10

A. 1/2

Question 11

Two projectiles are fired from the same point with the same speed at angles of projection 60° and 30° respectively.
Which one of the following is true?

A. Their landing velocity will be same
B. Their range will be same
C. Their time of flight will be same
D. Their maximum height will be same

Answer 11

B. Their range will be same

Question 12

Assuming a frictionless, massless
pulley, determine the acceleration of the
blocks once they are released from rest.

(P4Eng2 FIGURE)

A. (M-m)g/(M+m)
B. Mg/(m+M)
C. (M+m)g/(M-m)
D. Mg/m

Answer 12

A. (M-m)g/(M+m)

FT -mg=ma(1)
FT -Mg= M(-a)(2)
a=Mg-mg/M+m=M-mg/M+m

Question 13

The coefficient of static friction
between a box and a ramp is 0.5. The ramp’s incline angle is 30°. If the box is placed at rest on the ramp, the box will do which of the following?

A. Move with constant velocity down the
ramp.
B. Not move.
C. Accelerate briefly down the ramp but then
slow down and stop.
D. Accelerate down the ramp.

Answer 13

D. Accelerate down the ramp.

The force pulling the block down the
ramp is mg sin 0, and the maximum
force of static friction is μsFN = smg cos e. If mg sin θ is greater than usmg cos 0, then there is a net force down the
ramp, and the block will accelerate
down. So, the question becomes,”Is
sin θ greater than μs cos θ?” Since θ=
30° and ps = 0.5, the answer is “yes.”

Question 14

The average speed of a moving object
during a given interval of time is always.

A. the magnitude of its average velocity over
the interval
B. its acceleration multiplied by the time
interval
C. one-half its speed at the end of the interval
D. the distance covered during the time
interval divided by the time interval

Answer 14

D. the distance covered during the time
interval divided by the time interval

Question 15

A ball is in free fall. Its acceleration is:

A. downward during both ascent and
descent
B. downward during ascent and upward
during descent
C. upward during ascent and downward
during descent
D. upward during both ascent and descent

Answer 15

A. downward during both ascent and
descent

Question 16

Which of the following is NOT an
example of accelerated motion?

A. Vertical component of projectile motion
B. Horizontal component of projectile
motion
C. Earth’s motion about sun
D. Circular motion at constant speed

Answer 16

B. Horizontal component of projectile
motion

Question 17

A bullet shot horizontally from a gun:

A. strikes the ground much later than one
dropped vertically from the same point at
the same instant
B. travels in a straight line
C. never strikes the ground
D. strikes the ground at approximately the
same time as one dropped vertically
from the same point at the same
instant

Answer 17

D. strikes the ground at approximately the
same time as one dropped vertically
from the same point at the same
instant

Question 18

Three blocks (A,B,C), each having mass
M, are connected by strings as shown.
Block C is pulled to the right by a force F
that causes the entire system to
accelerate. Neglecting friction, the net
force acting on block B is:

A. F/2
B. Zero
C. 2F/3
D. F/3

Answer 18

D. F/3

(P4Eng2 FIGURE)

Question 19

A brick slides on a horizontal surface.
Which of the following will increase the
magnitude of the frictional force on it?

A. Putting a second brick on top
B. Decreasing the surface area of contact
C. Increasing the surface area of contact
D. Decreasing the mass of the brick

Answer 19

A. Putting a second brick on top

Question 20

Why do raindrops fall with constant speed during the later stages of their descent?

A. The force of gravity is negligible for
objects as small as raindrops
B. The gravitational force is the same for all
drops
C. Air resistance just balances the force of
gravity
D. The drops all fall from the same height

Answer 20

C. Air resistance just balances the force of
gravity

Question 21

The amount of work required to stop a
moving object is equal to:

A. the mass of the object times its velocity
B. the kinetic energy of the object
C. the mass of the object times its
acceleration
D. the velocity of the object

Answer 21

B. the kinetic energy of the object

Question 22

Momentum may be expressed in:

A. Kg/m
B. N-s
C. gram-s
D. kg/(m-s)

Answer 22

B. N-s

Question 23

The momentum of an object at a given
instant is independent of its:

A. Speed
B. Acceleration
C. Velocity
D. Mass

Answer 23

B. Acceleration

Question 24

Two objects, P and Q, have the same
momentum. Q has more kinetic energy
than P if it:

A. is moving slower than P
B. weighs the same as P
C. weighs more than P
D. is moving faster than P

Answer 24

D. is moving faster than P

Question 25

If the total momentum of a system is
changing:

A. the system must be under the influence of
gravity
B. the center of mass must have constant
velocity
C. particles of the system must be exerting
forces on each other
D. a net external force must be acting on
the system

Answer 25

D. a net external force must be acting on
the system

Question 26

Force:

A. equals the negative integral (with respect
to distance) of the potential energy
function
B. equals the time rate of change of
momentum
C. is the ability to do work
D. is the rate of change of doing work

Answer 26

B. equals the time rate of change of
momentum

Question 27

The physical quantity “impulse” has the
same dimensions as that of:

A. Energy
B. Power
C. Momentum
D. Force

Answer 27

C. Momentum

Question 28

Which is the correct statement about
law of polygon of forces?

A. if any number of forces acting at a
point can be represented in direction
and magnitude by the sides of a
polygon taken in order, then the forces
are in equilibrium
B. if any number of forces acting at a point
can be represented in direction and
magnitude by the sides of a polygon, then
the forces are in equilibrium
C. if any number of forces acting at a point
can be represented by the sides of a
polygon taken in order, then the forces are
in equilibrium
D. if a polygon representing forces acting at a
point is closed then forces are in
equilibrium

Answer 28

A. if any number of forces acting at a
point can be represented in direction
and magnitude by the sides of a
polygon taken in order, then the forces
are in equilibrium

Question 29

The algebraic sum of the resolved parts
of a number of forces in a given
direction is equal to the resolved part of
their resultant in the same direction.
This is as per the principle of

A. independence of forces
B. balance of force
C. resolution of forces
D. dependence of forces

Answer 29

C. resolution of forces

Question 30

According to principle of transmissibility
of forces, the effect of a force upon a
body is

A. the same at every point in its line of
action
B. different at different points in its line of
action
C. maximum when it acts at the center of
gravity of a body
D. minimum when it acts at the C.G. of the
body

Answer 30

A. the same at every point in its line of
action

Question 31

D’ Alembert’s principle is used for

A. reducing the problem of kinetics to
equivalent statics problem
B. stability of floating bodies
C. determining stresses in the truss
D. designing safe structures

Answer 31

A. reducing the problem of kinetics to
equivalent statics problem

Question 32

According to Lami’s theorem

A. if three forces acting at a point are in equilibrium, each force is proportional to the sine of the angle between the
other two
B. if three forces acting upon a particle are
represented in magnitude and direction by the sides of a triangle, taken in order, they will be in equilibrium
C. three forces acting at a point can be
represented by a triangle, each side being
proportional to force
D. three forces acting at a point will be in
equilibrium

Answer 32

A. if three forces acting at a point are in equilibrium, each force is proportional to the sine of the angle between the
other two

Question 33

The center of gravity of a triangle lies at
the point of

A. intersection of bisector of angles
B. intersection of its altitudes
C. concurrence of the medians
D. intersection of diagonals

Answer 33

C. concurrence of the medians

Question 34

Angle of friction is the

A. the ratio of minimum friction force to
friction force acting when the body is in
motion
B. ratio of limiting friction and normal
reaction
C. angle between normal reaction and the
resultant of normal reaction and the
limiting friction
D. the ratio of minimum friction force to the friction force acting when the body is just about to move

Answer 34

C. angle between normal reaction and the
resultant of normal reaction and the
limiting friction

Question 35

Frictional force encountered after
commencement of motion is called:

A. Post friction
B. Limiting friction
C. Dynamic friction
D. Kinematic friction

Answer 35

C. Dynamic friction

Question 36

A car of mass m is moving on a level
circular track of radius R. If μs
represents the static friction between
the road and tyres of the car, the
maximum speed of the car in circular
motion is given by:

A. √(μsRg)
B. √(μsmRg)
C. √(mRg/μs)
D. √(Rg/μs)

Answer 36

A. √(μsRg)

For smooth driving maximum speed of
car v then
mv/R=usmg
v=√usRg

Question 37

A ball is dropped from a satellite
revolving around the earth at a height of
120 km. The ball will:

A. fall down to earth gradually
B. go far away in space
C. continue to move with the same speed
along the original orbit of satellite
D. continue to move with same speed along a straight line tangentially to the satellite at that time

Answer 37

C. continue to move with the same speed
along the original orbit of satellite

The orbital speed of satellite is
independent of mass of satellite, so the
ball will behave as a satellite and will
continue to move with the same speed
in the original orbit.

Question 38

The centre of mass of a system of
particles does not depend upon:

A. position of the particles
B. forces acting on the particles
C. relative distances between the particles
D. masses of the particles

Answer 38

B. forces acting on the particles

Centre of mass of system depends
upon position and masses of particle Also, it depends upon relative distance between particles.

Question 39

Which of the following is not a vector
quantity?

A. Work
B. Displacement
C. Electric field
D. Acceleration

Answer 39

A. Work

Question 40

particle of mass M is moving in a
horizontal circle of radius R with
uniform speed V. When it moves from one point to a diametrically opposite point, its:

A. kinetic energy changes by MV^2/4
B. kinetic energy changes by MV^2
C. momentum does not change
D. momentum changes by 2 MV

Answer 40

A. kinetic energy changes by MV^2/4

On the diametrically opposite points, the
velocities have same magnitude but
opposite directions. Therefore, change
in momentum is MV-(-MV) = 2MV

Question 41

When milk is churned, cream gets
separated due to:

A. Frictional force
B. Centrifugal force
C. Gravitational force
D. Centripetal force

Answer 41

B. Centrifugal force

Question 42

Two racing cars of masses m1 and m2
are moving in circles of radii r1 and r2
respectively. Their speeds are such that
each makes a complete circle in the
same time t. The ratio of the angular
speeds of the first to the second car is:

A. m1m2:r1r2
B. m1:m2
C. 1:1
D. r1:r2

Answer 42

C. 1:1

As time taken by both car to complete
one revolution is same.
As w=2n/T→ wo1/T, as T is same in
both cases. Hence ‘w’ will also be same.