

SAT Physics - Work and Energy
Exam Duration: 45 Mins Total Questions : 30
The K.E of a body is increased most by doubling its
- (a)
mass
- (b)
density
- (c)
speed
- (d)
weight
What is the momentum of a body of mass 100 g having a K.E. of 20 J
- (a)
2kg ms-1
- (b)
1/2 kg ms-1
- (c)
2g cms-1
- (d)
none of these
A horse and a dog are running with the same speed. If the mass of horse is 20 times than that of a dog, what is the ratio of their kinetic energy
- (a)
20:1
- (b)
5:1
- (c)
10:1
- (d)
2:1
A girl of mass 50 kg runs up a flight of 40 stairs each measuring 20 cm in 50 s, the power of the girl utilise while running upstairs is equal to
- (a)
40 w
- (b)
60 w
- (c)
100 w
- (d)
80 w
If a body is moving with a velocity of 4 m/s for 15 s the work done by the body is
- (a)
60 J
- (b)
zero
- (c)
3.8 J
- (d)
0.35
The P.E. of a body at a certain height is 200 J.The kinetic energy possessed by it when it just touches the surface of the earth is:
- (a)
P.E.
- (b)
< P.E.
- (c)
= P.E.
- (d)
Cannot be known
If the speed of an object is doubled, then its kinetic energy is ______
- (a)
Doubled
- (b)
Quadrupled
- (c)
Halved
- (d)
Tripled
If air resistance is negligible, the sum total of potential and kinetic energies of a freely falling body ______
- (a)
Increases
- (b)
Decreases
- (c)
Becomes zero
- (d)
Remains the same
An iron sphere of mass 10 kg has the same diameter as an aluminium sphere of mass is 3.5 kg. Both spheres are dropped simultaneously from a tower. When they are 10 m above the ground, they have the same
- (a)
Acceleration
- (b)
Momentum
- (c)
Potential energy
- (d)
Kinetic energy
An object at rest may have
- (a)
Speed
- (b)
Velocity
- (c)
Energy
- (d)
Momentum
A heavy and a light object released from the same height in a vacuum have equal :
- (a)
Weights
- (b)
Energies
- (c)
None of these
- (d)
Momentum
Force F acts on a body such that force F makes an angle θ with the horizontal direction and the body is also displaced through a distance S in the horizontal direction, then the work done by the force is:
- (a)
Fs
- (b)
Fs cos θ
- (c)
Fs sin θ
- (d)
zero
In tug of war work done by winning team is:
- (a)
zero
- (b)
positive
- (c)
negative
- (d)
none of these
In tug of war work done by loosing team is:
- (a)
zero
- (b)
positive
- (c)
negative
- (d)
none of these
When you compress a spring you do work on it. The elastic potential energy of the spring:
- (a)
increases
- (b)
decreases
- (c)
disappears
- (d)
remains constant
An object of mass 10 kg falls from height 10m. Kinetic energy gained by the body will be approximately equal to:
- (a)
1000 J
- (b)
500 J
- (c)
100 J
- (d)
None of these
The potential energy of a boy is maximum when he is:
- (a)
standiny
- (b)
sleeping on the ground
- (c)
sitting on the ground
- (d)
sitting on chair
The potential energy of a freely falling object decreases continuously. What happens to the loss of potential energy?
- (a)
it is continuously converted into sound energy
- (b)
it is continuously converted into kinetic energy
- (c)
It is continuously destroyed
- (d)
None of these
When a long spring is stretched by 2 cm, its potential energy is u. If the spring is stretched by 10 cm, the potential energy stored in it will be
- (a)
25 u
- (b)
\(\frac{u}{25}\)
- (c)
5u
- (d)
\(\frac{u}{5}\)
In the above example, the work done is minimum when the body is
- (a)
pushed over an inclined plane
- (b)
lifted vertically upward
- (c)
pushed over the smooth rollers
- (d)
pushed on a plane horizonal surface
A body moves through a distance of 3m in the following different ways.The extra power required is
- (a)
0.04 W
- (b)
0.08W
- (c)
0.4W
- (d)
0.4W
The relationship between force and position is shown in the figure (in one dimensional case). Work done by the force is displacing a body from x = 1 cm to x = 5 cm is
- (a)
700 ergs
- (b)
70 ergs
- (c)
60 ergs
- (d)
20 ergs
Work done by a centripetal force
- (a)
increases by decreasing the radius of the circle
- (b)
decreases by increasing the radius of the circle
- (c)
increases by increasing the mass of the body
- (d)
is always zero
Which of the following physical quantity is different from others?
- (a)
Work
- (b)
Kinetic energy
- (c)
Force
- (d)
Potential energy
A tennis ball dropped from a height of 2 m rebounds only 1.5 m after hitting the ground. What fraction of energy is lost in the impact?
- (a)
\(\frac{1}{4}\)
- (b)
\(\frac{1}{8}\)
- (c)
\(\frac{1}{2}\)
- (d)
\(\frac{1}{16}\)
Work is always done on a body when
- (a)
a force acts on it
- (b)
it moves through a certain distance
- (c)
it experiences an increase in energy through a mechanical influence
- (d)
none of the above
The kinetic energy of an objective of mass 1 kg is 200 J, The velocity of this objects
- (a)
\(\sqrt{200}\) m/s
- (b)
10 m/s
- (c)
20 m/s
- (d)
40 m/s
Work done by frictional force is designated as
- (a)
infinity
- (b)
zero
- (c)
positive
- (d)
negative
A stone of mass m is moved in a circle of radius r with constant speed V. The work done by the force over half the circumference of the circle is
- (a)
zero
- (b)
\(\frac{mv^{2}}{r}\times \pi r\)
- (c)
\(\frac{mv^{2}}{r}\times 2\pi r\)
- (d)
mgx2πr
KE. of an object is proportional to
- (a)
its velocity
- (b)
its weight
- (c)
its momentum
- (d)
square of its velocity