A student investigates how a crumple zone affects the average force exerted on a vehicle during a collision.
They set up a dynamics cart of mass m m\,m on a sloping ramp directed towards a solid barrier. Specifically, they compare two setups: one cart with a rigid plastic bumper, and another cart with a soft, compressible foam bumper representing a crumple zone.
The student releases the cart from a fixed point on the ramp. Just before impact, the cart passes through a light gate to measure its velocity. On impact with the barrier, the cart is brought to a complete stop.
Two thin copper contact strips (one on the bumper, one on the barrier) complete a circuit on contact, allowing a millisecond timer to record the exact duration of the collision.
Explain how the student could carry out this investigation to compare the effect of the two bumpers on the average force exerted during the collision. Your explanation should include:
- How to determine the average force (suggesting key measurements and any necessary physical equations)
- How the benefit of the crumple zone is demonstrated by the results
- Precautions and control variables needed to ensure accurate and valid results