1.21 use the idea of momentum to explain safety features

force = change in momentum / time

safety features aim to reduce the force acting upon the human. If the momentum of the vehicle is decreased, the force felt by the human will decrease. similarly, if the time taken for momentum to change is increased, the overall force is decreased.

crumple zones in cars are designed to decrease the time it takes for the momentum of the car to reach zero, this will result in the passenger feeling less force

air bags also decrease the force felt by the passenger


to understand better (don't write in exam!)...

if you jump with your knees locked on landing, you will feel more force than if you jumped with your knees bent on landing. You feel less force when your knees are bent because you take more time to reach zero momentum than if your knees are locked... try it :)