Momentum and Collisions
It has been suggested by some that the concept of momentum is more intuitive and accessible for students to grasp than acceleration and some courses have been designed to introduce momentum before acceleration. When studying motion it is common for students to muddle and merge speed, velocity and acceleration into ‘movement’ and not adequately differentiate between them. The view of the ‘momentum first’ teaching approach is partly that that momentum is more accessible as a measurement of ‘movementness’ rather than the rate of change of a rate of change (i.e. acceleration). Either way, there is a message here for teachers about making sure we are clear and separate these overlapping ideas otherwise the students will struggle.
It is very common for questions to all be about trucks and cars and if we leave aside the potential gender bias here there is a danger that students can see the measurement and conservation of momentum as a specific and not universal thing, so a variation of contexts is encouraged. Students will benefit from plenty of practice with calculations and equations, like those given here and it's also great to bring the topic right up to date with the computing and space station contexts.
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Links and Resources
Richard Garriott may not be the best person in the world at explaining conservation of momentum but he does have a simply amazing classroom. While most of us have to make do with a linear air track if we’re lucky, he has the International Space Station at his disposal! You could use this film after teaching the topic more conventionally to illustrate what you have been explaining or try showing the film with the sound turned down and asking your students to write the script – it could be better than Richard’s!
Once you’ve got the hang of how this set of resources is organised, you’re likely to find them really useful, particularly if you are teaching outside your specialism. As we’ve come to expect from the IOP (Institute of Physics) the physics is really well explained and teachers will appreciate the tips about how to get around common misconceptions. Of relevance to this topic are the Measures of Quality of Motion resources which deal with the concept of momentum and suggest some really thought provoking demonstrations and experiments.
This rather eclectic collection of problems and calculations from ESA (the European Space Agency) provide real life data and some excellent space contexts. Although unlikely to be used in its format here, teachers might like to include some of the activities when providing students with practise at using and applying the equations they have been taught. For example exercise 9, Space Debris provides a powerful example of momentum in action.
This historical crash provides a real life context in which students can apply their knowledge and skills. Although the activity is not linked directly to the GCSE specifications, it is worth using as an extension activity if time permits since is also brings home very clearly how science works, scientific evidence and the tentative nature of any conclusions. As it stands it’s suitable for well-motivated and capable students but weaker students are likely to need more support and guidance than is offered here.
A lovely starter to a lesson on momentum or conservation of momentum, this two and half minute film documents the first ever space walk where Ed White manoeuvres himself around with a hand held oxygen jet. Let students know that the film is speeded up but without further teacher comment ask your students to speculate how old the film is and then discuss how the astronaut is able to control his movement.
More experienced teachers will find this resource reminiscent of the text books they used at school! However, chapter four is a really interesting take on changes in motion and is worth looking through. The investigation recommended here is investigation 8.4 on page 57 of the pdf document. This mathematical treatment of rocket propulsion will suit some able students down to the ground and they may find it helpful to complete the calculations using a spreadsheet. Other students will need more support since it is quite demanding conceptually and with these students it might be sensible to give them to the data for the speed of the rocket and get them to plot it against its mass. Challenge them to explain how the decreasing mass has caused the increase in speed.
see notes with resource above
This 7 min film is great for showing both physics and exciting physics linked careers. Computer games go out of date rapidly so use this resource now while it’s hot! The back end of the film deals with momentum and collisions but it’s worth watching the whole film as a lesson starter as it recaps the work on forces that you want students to be familiar with. It’s super for showing physics in action. Just one complaint – no women!
Using equations and carrying out calculations are an integral part of physics. Here are some useful worked examples and questions about momentum which will save teachers having to write their own. They are on pages 16-18 of the book (pages 24-26 of the pdf document). Depending on the ability of the class, teachers might like to talk through the worked examples on the board before setting the questions. The answers are on page 125 (pdf page 133)