Work in Physics: A Detailed Explanation

Understanding Work

If the force and displacement are in the same direction, the entire force contributes to the work. However, if they are not parallel, only the component of the force parallel to the displacement contributes to the work. This means that when a force acts on an object and causes it to move, work is done. The amount of work done depends on two key factors:

  1. Force: The magnitude of the force applied.

  2. Displacement: The distance the object moves in the direction of the force.

Mathematical Representation

The formula for calculating work is:

Work = Force × Displacement


Force and Displacement Direction

If the force and displacement are in the same direction, the entire force contributes to the work done. However, if they are not parallel, only the component of the force that is parallel to the displacement contributes to the work.

Units of Work

The SI unit of work is the joule (J). One joule is the amount of work done when a force of one newton displaces an object through one meter in the direction of the force.

Example: Carrying a Bag Upstairs

To illustrate the concept of work, let's consider the example of a girl carrying a 10 kg bag upstairs.

  1. Calculate the weight of the bag: Weight = mass × gravity = 10 kg × 10 m/s² = 100 N.

  2. Determine the total height: 18 steps × 20 cm/step = 360 cm = 3.6 m.

  3. Calculate the work done: Work = Force × Displacement = 100 N × 3.6 m = 360 J.

Therefore, the girl does 360 joules of work in carrying the bag upstairs.

Key Points

  • Work is a scalar quantity, meaning it has magnitude but no direction.

  • The unit of work is the joule (J).

  • Work is done when a force causes an object to move in the direction of the force.

  • The amount of work depends on the magnitude of the force and the displacement in the direction of the force.

  • The work done by a force on an object is equal to the product of the component of the force parallel to the displacement and the displacement.

By understanding these concepts, you can better grasp the principles of work in physics and apply them to various real-world situations.