Work Done | Physics for Grade 10 PDF Download

Introduction

• Work is done when an object is moved over a distance by a force applied in the direction of its displacement
  • It is said that the force does work on the object
  • If a force is applied to an object but doesn’t result in any movement, no work is done
    
    Work is done when a force is used to move an object

Examples of Work

• Work is done on a ball when it is lifted to a height above the ground
  
  The weight on the ball produced by the gravitational field does work on the ball over a distance equal to the height of the ball
• Work is done when a bird flies through the air
  
  Air resistance (drag) does work against the bird as it flies through the air

Calculating Work Done

• The amount of work that is done is related to the size of the force and the distance moved by the object in the direction of the force
• To calculate the amount of work done on an object by a force the following formula is used
  W = F × s
• Where:
  • W = work done in Joules (J) or newton-metres (N m)
  • F = force in Newtons (N)
  • s = distance in metres (m)
• This equation can be rearranged with the help of a formula triangle

Solved Example

Example: A car moving at speed begins to apply the brakes. The brakes of the car apply a force of 500 N which brings it to a stop after 23 m.
Calculate the work done by the brakes in stopping the car.

Step 1: List the known quantities
Distance, s = 23 m
Force, F = 500 N

Step 2: Write out the equation relating work, force and distance
Work = F × s

Step 3: Calculate the work done on the car by the brakes
Work = 500 × 23 = 11 500 J