WHAT IS WORK DONE AND CALCULATION OF WORK DONE

MECHANICAL TIPS AND STUDY MATERIAL

When any energy or force is applied on body and it moves by certain distance, then work is said to be done. In other words motion producing force creates work. Examples of work are 

1) pulling/pushing of box on ground.
2) Hitting of ball with bat. Etc

Factors that effects the work done

1) Magnitude of force
2) In direction of force the distance moved by body.

In physics work is product of force and distance moved.
                        W = F x D
Where W is work
F is Force applied
D is distance moved

The unit of work is joule. Joule is N-m (product of force x distance).

Definition of Joule

When one newton of force moves a body by one metre distance, then work done is said to be one joule.

1Joule = 1Newton x 1metre
Joule is scaler quantity. 

If you apply force on an object and it doesn't move then work done is zero.


Calculation of work done

• By gravity
• By the force acting opposite to the direction of motion
• By force acting in oblique direction
• By force acting in right angle to the direction of motion

By gravity

When you lift an object against the ground, you are doing work against gravity. When body is lifted vertically upwards the force required to lift it is equal to its weight. The amount of work done is equal to product of weight of body and vertical distance by which body has moved.

Let W be the work done, m be the mass, g is gravity and h is the height moved. Collectively mg is known as weight.

                        W = m x g x h

By the force acting in opposite direction of motion

This is the case of negative work done. When a force is applied in direction opposite to the motion of the body, then work is said to be negative. If this is the case then the force acting is given by negative sign (-F). Hence work done is given as

                 W = (-F) x S

By force acting in oblique direction

In such condition the force is not exactly along the direction of motion but it is at some angle. Realize a situation with an example. Consider a car toy tied with strings on one end and the other end a child holds it and pulls. He is applying force through string. The body moves in horizontal direction by the component of force acting along that direction. The force component acting perpendicular to the motion zero as because cos 90° is always zero.