Question

You have been called in by your neighborhood safety council to advise them about installing a barrier on a dangerous curve that has been subject to several recent accidents. They need to decide between a new a "softer barrier", which consists of barrels of water, and the traditional concrete barrier. In a test, two 1400 kg cars initially travelling at 50 mph were crashed into each barrier. The softer barrier took 1.6 s to bring the car to a rest, while the traditional barrier took 0.1. You have been asked to prepare a report on the force exerted on the car in each case.

Answer 1

Answer: The softer barrier is the better option

Explanation:

1) When is a car is moving at a certain speed, it has a certain amount of momentum (p=mv). A collision against a barrier would cause its momentum to decrease to 0. A change in momentum is Impulse

2) The formula for Impulse: J = f * Δt

J is Impulse

f is the force applied during the time Δt

A tough barrier would produce a smaller Δt, which means more force is applied on the car. (J is always constant)

A softer barrier would apply less force on the car, which means Δt is large.

Answer: The softer barrier is the better option