A couple of physics questions on helmets!? 1. Why is the impact force reduced for a helmet with a soft interior vs.a hard interior? 2. How is the safety reduced if the helmet does not fir properly? 3. Once a helmet has been involved in a collision, it should be replaced. why? 4. What sort of collision will be caused if a helmet collides with an objects? will it be an elastic, inelastic, or a completely inelastic collision? and why?