Practise using efficiency to calculate useful output, total input or wasted energy and power, solving multi-step transfers and interpreting the difference.
A child's toy uses the spring in (a) to launch a ball of mass 0.020 kg vertically into the air. The ball is initially held against one end of the spring which has a compression of 0.045 m . The spring is then released to launch the ball. The kinetic energy of the ball as it leaves the toy is 0.72 J .
The toy converts the elastic potential energy of the spring into the kinetic energy of the ball. Use the information in (a)(ii) to calculate the percentage efficiency of this conversion.
efficiency =(0.72/0.81)×100=89%
A1