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Q 01 / 25
Work is said to be done only when a force is applied on an object and the object is displaced.
Q 02 / 25
If there is no displacement, work done is zero even if a large force is applied.
Q 03 / 25
Work can be positive, negative, or zero.
Q 04 / 25
When a coolie carries a load on his head and walks horizontally, he does positive work on the load.
Q 05 / 25
Work done against gravity in lifting an object is stored as potential energy in the object.
Q 06 / 25
Kinetic energy depends on both mass and velocity of the object.
Q 07 / 25
Potential energy of an object does not depend on the height of the object.
Q 08 / 25
The SI unit of work is joule (J).
Q 09 / 25
A body moving with uniform velocity does no work against friction.
Q 10 / 25
Power is the rate of doing work.
Q 11 / 25
The SI unit of power is watt.
Q 12 / 25
Energy and work have the same unit.
Q 13 / 25
When work is done on an object, its energy decreases.
Q 14 / 25
The sum of kinetic and potential energies of a body is called its total mechanical energy.
Q 15 / 25
In the absence of friction, the total mechanical energy of a system remains constant.
Q 16 / 25
The work done by gravity on a freely falling body is positive.
Q 17 / 25
The work done by friction is always positive.
Q 18 / 25
The commercial unit of energy is kilowatt-hour (kWh).
Q 19 / 25
If a body is moving horizontally, its potential energy changes continuously.
Q 20 / 25
Energy can neither be created nor destroyed; it can only change from one form to another.
Q 21 / 25
When a ball hits the ground and bounces back, energy is completely lost.
Q 22 / 25
Work done on an object is independent of the direction of force.
Q 23 / 25
When an object is thrown upwards, its kinetic energy increases with height.
Q 24 / 25
The power of a machine tells us how fast it can do work.
Q 25 / 25
A boy climbs a staircase slowly and another runs up quickly; both do the same work but have different power.
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