Work and Energy

Work is done when the force produces motion.The work done by a force on a body depends on two factors: I) Magnitude of force II) Distance through which the body moves

Definition of work:

Work is said to be done when the point of application of a force moves.Work done in moving a body is equal to the product of force exerted on the body and the distance moved by the body in the direction of force.

Work = Force x Distance moved in the direction of force

Unit of work:

The unit of work is Newton metre Which is written as Nm

When force of 1 Newton moves a body through a distance of 1 metre in its own direction ,then the work done is known as 1 joule. 1 joule = 1 Newton x 1 metre =1Nm

Definition of Power:

Power is defined as the rate of doing work.

Power = Workdone / Time taken

P = W / T

Hence, power is the work done per unit time. Power is scalar quantity.

Unit of power:

S.I unit of power is watt and it is the rate of doing work at 1 joule per second.

1 watt= 1 joule / 1 second

Energy:

The ability to do work.

The amount of energy possessed by a body is equal to the amount of work it can do when its energy is released.

S.I unit of energy is joule.Energy is a scalar quantity.

Mechanical energy is of two types:

• Kinetic energy
• Potential energy

Kinetic energy:

The energy of a body due to its motion.

Formula for kinetic energy

K.E = ½ mv²

where m-mass of the body v-velocity of the body

Potential energy:

The energy of a body due to its position or change in its shape is known as potential energy. Body may possesses energy even when it is not in motion.

Formula for potential energy

P.E= m x g x h where m - mass of the body g- acceleration due to gravity h-height of the body above reference point.

Mechanical energy :

Sum of P.E and K.E of a body is called its mechanical energy.