Learn It: Sample Questions Using the Work Equation

Question 1

Calculate the work done when a force of 10 newtons acts through a distance of 50 metres in the direction of the force.

Worked solution:

   W = Fs
       = 10 × 50
       = 500 J                 Ans.  500 J

Question 2

A girl pulls a sledge a distance of 100 metres. If the force exerted by the girl is 80 newtons in the direction in which the sledge is moving, calculate the work done.

Worked solution:

   W = Fs
       = 80 × 100
       = 8000 J
       = 8 kJ                   Ans.  8 kJ

Question 3

A car of mass 900 kg accelerates at 3 ms-2 from rest. How much work is done after it has travelled 100 metres? 

Worked solution:

There are two steps involved in solving this problem:

Step 1 :  Calculate the force required to cause the acceleration.

    Recall: Force = mass × acceleration

   F = ma
   F = 900 × 3
   F = 2700 N

Step 2 :  Then use the work equation.  

  W = Fs
     = 2700 × 100
     = 270 000 J
     = 270 kJ                     Ans.  270 kJ

In Unit 2 you will learn an even quicker way to solve this type of problem.

Next: Learn It - Lifts and Escalators