WORK,ENERGY & POWER

SHAHBAZ AHMED15CH44

Work:• When a force acts on a body in such a way that body covers some

displacement, it is called work.• Work(W) is defined as a product of force(F) and displacement(d)

• Work can be defined as transfer of energy. • Work is scalar quantity. • InSI unit of work is Joule( J ). J=N×m• If force makes an angle with the direction of motion, then for finding

work done, that component of force will be taken which acts in the direction of motion(Fcos ) .W=F cos d

• W=F cos d

Continue…• (A) When direction of force and displacement is same the work

done is positive

• (B) When direction of force and displacement is opposite the work done is negative.

• (C) When force and displacement are mutually perpendicular to each other the work done is zero.

POWER :• The rate of doing work is known as power.

Power= • Power is a scalar quantity.• Unit of Power is watt or J/s.• Other common unit is horse power.• 1hp=746Watt.

Energy:The ability of doing work is called Energy.In SI units energy is measured in Joule(J).Energy is scalar quantity.

ENERGY

Mechanical Non- Mechanical

Kinetic Potential

Linear

Rotational

Gravitational

Elastic

Electric

Magnetic

Light

Sound

Heat

Law of Conservation of energy• Statement=Energy is neither created nor destroyed, but one form of

energy is converted into an other form of energy, so total energy of the system remains constant.• Explanation= In an isolated system from the motion of the

pendulum above law of conservation of energy is proved in following way.

P.E=100J K.E= OJ

P.E= O JK.E = 100 J

AB