Unit 3E Magnets and Springs

Unit 6E: Forces in action

Bungee jumping

Materials needed a selection of elastic material metre ruler recording page / pencil toy (eg teddy, doll, action man) scales scissors chair/window ledge for bungee launch for a drop of about 1m

Pupils need to select a toy that they can easily attach elastic to for bungee jumping. They need to select and try different elastic material that would be most appropriate to give a rebound and not hit the ground. The "pull" force is exerted by the elastic in one direction and gravity in the other. The "push" force comes mass of the toy.

In their explanation children need to emphasise the push / pull nature of the forces. This is seen clearly in the rebounding action of the bungy jump.

Questions to answer: What is the mass of the toy? What force will be exerted by the toy as it drops? Possible activities  Find a drop of approximately 1m around the class for the bungy launch  Measure and cut 10 cm of elastic or rubber bands for stretch test  Give a gentle pull on the elastic beside a ruler and decide how far it will stretch, record the stretch. When you pull, feel the force which is reacting back on the elastic.  Make an estimate from the stretch and work out approximately how much elastic you will need for your toy to bungy 1m ( this is variable, you can use higher if you have more elastic!)  You will need to tie a length of elastic onto the toy and experiment to get the correct length  Do not cut the elastic until you have completed the testing!  The toy needs the maximum jump length closest to a metre, but it must be safe and not touch the ground  Record the length of the elastic you use  You might like to test a range of elastic cord material to explore which will give the best rebound and record the stretch  Do the final test of the bungy jump, talk about the push and pull forces  Discuss the results  Make the links between bungy jumping, gravity and forces for the teaching of this concept of forces Unit 6E: Forces in action

Select a toy that you can easily attach elastic to for bungee jumping. Try different elastic material that will give a rebound and not hit the ground. The "pull" force is exerted by the elastic in one direction and gravity in the other. The "push" force comes mass of the toy.

Materials needed a selection of elastic material metre ruler recording page / pencil toy (eg teddy, doll, action man) scales scissors chair/window ledge for bungee launch for a drop of about 1m

Record your results on a sheet like this

Recording Sheet

Length of Mass of toy elastic Prediction Stretch of elastic material Stretch 1 Stretch 2 Stretch 3

 What is the mass of the toy?  What force will be exerted by the toy as it drops?  Were your predictions correct?  Discuss the results  Can you explain the links between bungy jumping, gravity and forces? Help sheet

Possible activities

 Find a drop of approximately 1m around the class for the bungy launch  Measure and cut 10 cm of elastic or rubber bands for stretch test  Give a gentle pull on the elastic beside a ruler and decide how far it will stretch, record the stretch. When you pull, feel the force which is reacting back on the elastic.  Make an estimate from the stretch and work out approximately how much elastic you will need for your toy to bungy 1m ( this is variable, you can use higher if you have more elastic!)  You will need to tie a length of elastic onto the toy and experiment to get the correct length  Do not cut the elastic until you have completed the testing!  The toy needs the maximum jump length closest to a metre, but it must be safe and not touch the ground  Record the length of the elastic you use  You might like to test a range of elastic cord material to explore which will give the best rebound and record the stretch  Do the final test of the bungy jump, talk about the push and pull forces  Discuss the results  Make the links between bungy jumping, gravity and forces for the teaching of this concept of forces