A student investigates collisions between two trolleys on a level track. Table shows the student's results.
Table: The total momentum of two trolleys measured before and after four collisions
| Collision | Total momentum before in kg m/s\text{kg m/s}kg m/s | Total momentum after in kg m/s\text{kg m/s}kg m/s |
|---|---|---|
| W | 1.20 | 0.96 |
| X | 1.44 | 1.44 |
| Y | 0.88 | 0.72 |
| Z | 2.05 | 1.60 |
The student concludes that momentum is not always conserved. Which is the best reason why the results do not support this conclusion?
friction acted on the trolleys, so the trolleys were not a closed system
momentum is conserved only when the two colliding trolleys join together
the light gates measured the speed and not the velocity of the trolleys
momentum is conserved only when the total kinetic energy is unchanged
40 exam-style questions on AQA GCSE Physics 5.7 Momentum (HT only), covering 5.7.1 Momentum is a property of moving objects, 5.7.2 Conservation of momentum, and 5.7.3 Changes in momentum. Each one has a worked solution and a mark scheme showing where the marks go.