Work

Work

Work is done when a force pushes or pulls a load through a certain distance. For work to occur, it is essential that the force causes movement in its direction.

Key Concepts

1. Definition: Work is the outcome of a force lifting or moving a load through some distance.

2. Condition for Work:

   • A force must cause movement.
   • The movement must occur in the direction of the applied force.

Formula for Work

Examples of Work

1. Work is done:

   • When you lift a chair and put it on your head, you are doing work.
   • If someone else lifts the chair and puts it on your head, they are doing the work, not you.

2. No work is done: If you push a wall with great force but the wall does not move, no work is done because there is no movement in the direction of the applied force.

Unit of Work

The unit of work is joule (J).

1. Definition: 1 joule is the amount of work done when a force of 1 newton pushes or pulls something through a distance of 1 metre.

2. Example: If a force of 1 newton moves an object 1 metre, the work done is 1 joule.

Calculation of Work Done

A person pushes a barrel through a distance of 6 metres using 10 newtons. How much work is done by the person?

Solution:

Formula: $\text{Work Done} = \text{Force} \times \text{Distance}$

Given: Force = 10 N Distance = 6 m

Work = $10 \times 6 = 60$ Nm = 60 J

Therefore, the amount of work performed by the person is 60 joules.

Example 2

A mechanic used a force of 50 N to lift a car component, thereby doing 75 J of work. What was the distance moved by the car component?

Solution:

Formula: $\text{Distance} = \frac{\text{Work}}{\text{Force}}$

Given: Force = 50 N Work = 75 J

Distance = $\frac{75}{50} = 1.5$ m

Therefore, the mechanic lifted the car component through a distance of 1.5 metres.

Example 3

Suppose the work done by wind to move an empty tin through a distance of 20 m in its direction is 100 J. Find the force of the wind.

Solution:

Formula: $\text{Force} = \frac{\text{Work}}{\text{Distance}}$

Given: Work = 100 J Distance = 20 m

Force = $\frac{100}{20} = 5$ N

Therefore, the force exerted on the empty tin by the wind is 5 newtons.