work and energy

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

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

• (a) $0\degree$

• (b) $45\degree$

• (c) $90\degree$

• (d ) $180\degree$

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) momenta

• (c) potential energy

• (d) kinetic energy

Which one of the following is not the unit of energy?

• (a) joule

• (b) newton metre

• (c) kilowatt

• (d) kilowatt hour

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

Water stored in a dam possesses

• (a) no energy

• (b) electrical energy

• (c) kinetic energy

• (d) potential energy

A body is falling from a height h. After it has fallen a height  $\frac{h}{2}$   , 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

The number of joules contained in 1kWh is

• $36\times10^{6\ ^{ }}J$

• $3.6\times10^{7^{ }}J$

• $3.6\times10^{6^{ }}J$

• $3.7\times10^{7^{ }}J$

Two army persons A and B each of weight of 500N climb up a rope through a height of 10m.

A takes 20s while B takes 40s to achieve this task. what is ratio of the power of person A and B?

• 1:2

• 1:4

• 2:1

• 14:1

If speed of a car becomes 2 times, its kinetic energy becomes

• 4 times

• 8 times

• 16 times

• 12 times