Question

Define

(1) Work (2) Energy (3) Power

(4) Kinetic energy (5) Potential energy

Answer 1

(1) Work:

Work is said to be done when a force produces a displacement in the body and acts in any direction except perpendicular to the direction of displacement.

Work = Force × Displacement

SI unit of work is ‘joules’.

(2) Energy:

Capacity to do work is called energy. For example, an 18-year old man has more capacity to do work (like lifting a table) than a 6-year old child. SI unit of energy is ‘joules’.

(3) Power:

Power is the rate of doing work or the rate of transfer of energy. If W is the amount of work done in time t, then power is given by the expression,

It is expressed in watt (W).

(4) Kinetic energy:

Kinetic energy is the energy possessed by a body by the virtue of its motion. A body uses kinetic energy to do work. Its SI unit is ‘joules’.

Expression for kinetic energy,

Kinetic energy of hammer is used in driving a nail into a log of wood. Kinetic energy of air is also used to run wind mills.

(5) Potential energy:

Energy of a body possessed by virtue of its configuration or position is called potential energy. Its SI unit is ‘joules’.

Expression for gravitational potential energy,

U = mgh

Where, m = mass of the object

g = acceleration due to gravity

h = height of the object from reference line