Bouncy Plastic Bag Ball Challenge

As part of the Rubbish Science Use Rubbish – Create Something Useful – Learn Scientific Thinking this challenge is to create the bounciest ball possible just using newspaper, plastic bags and string.

Before we start though we need to consider why things bounce. Objects that can be compressed and then spring back quickly are bouncy. Rubber balls, springs etc. or pogo sticks. 

As a pogo stick falls it accelerates due to the force of gravity. When it hits the ground the pogo stick exerts a force on the ground compressing it. Using Newton’s Third Law the ground exerts an equal and opposite force on the pogo stick that also causes it to be compressed or squashed. Both the ground and the pogo stick spring back to their original shape and it is this that creates the upward force that accelerates the pogo stick upwards. If we apply this to the ball we are making. If the ball is very soft then it will not spring back very well and so wont bounce very high. If it is very hard it will not compress very much and so wont bounce very high.  The challenge is to find the optimum combination using only the materials provided.  You can make any size ball you like – golf ball to basketball size. The only limitations are with the materials that you use. To make this a fair challenge for everyone the ball should be dropped from a height of 1 metre onto a hard surface. Ideally a video or screenshot will show how high the ball bounced. 

Heather Sharp