Question 1.

When a body falls freely towards the earth, then its total energy
(a) increases
(b) decreases
(c) remains constant
(d) first increases and then decreases

Answer: (c) remains constant

Question 2.
A car is accelerated on a levelled road and attains a velocity 4 times of its initial velocity. In this process the potential energy of the car

(a) does not change
(b) becomes twice to that of initial
(c) becomes 4 times that of initial
(d) becomes 16 times that of initial

Answer: (a) does not change

Question 3.
In case of negative work the angle between the force and displacement is

(a) 0°
(b) 45°
(c) 90°
(d) 180°

Answer: (d) 180°

Question 4.
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 lo m above the ground, they have the same.

(a) acceleration
(b) momenta
(c) potential energy
(d) kinetic energy

Answer: (a) acceleration

Question 5.
A girl is carrying a school bag of 3 kg mass on her back and moves 200 m on a levelled road. The work done against the gravitational force will be (g = 10 ms²)

(a) 6 × 10³ J
(b) 6 J
(c) 0.6 J
(d) zero

Answer: (d) zero

Question 6.
Which one of the following is not the unit of energy?

(a) joule
(b) newton metre
(c) kilowatt
(d) kilowatt hour

Answer: (c) kilowatt

Question 7.
The work done on an object does not depend upon the

(a) displacement
(b) force applied
(c) angle between force and displacement
(d) initial velocity of the object

Answer: (d) initial velocity of the object

Question 8.
Water stored in a dam possesses

(a) no energy
(b) electrical energy
(c) kinetic energy
(d) potential energy

Answer: (d) potential energy

Question 9.
A body is falling from a height h. After it has fallen a height h/2, it will possess

(a) only potential energy
(b) only kinetic energy
(c) half potential and half kinetic energy
(d) more kinetic and less potential energy

Answer: (c) half potential and half kinetic energy

Question 10. The number of joules contained in 1 kWh is

(a) 36 × 105 J
(b) 3.6 × 107 J
(c) 36 × 108 J
(d) 3.7 × 107 J

Answer: (a) 36 × 10^5 J