Crash Victims Info

Average force in N exerted on the car by the barrier of a crash test?

You are the design engineer in charge of the crashworthiness of new automobile models. Cars are tested by smashing them into fixed, massive barriers at 30 mph. A new model of mass 1500 kg takes 0.095 s from the time of impact until it is brought to rest. Calculate the average force in N exerted on the car by the barrier.

Public Comments

1. j=ft=mchange in v f*.095=1500*30*1609/3600 F=211710 N *I changed this, The first time I answered I red quickly and did not change mph to m/s*** Sorry If you can increase the time, you can decrease the force that is why they make soft barriers such as water filled plastic barrels.
2. As a note: I did the conversion for 30mph to m/s. 30mi/h = 13.41m/s There's a theorem in Physics learned while you're focusing on momentum, and it's called the impulse-momentum theorem. Really, all it states is that the impulse from an object striking another is equal to the object's momentum before striking another object. Impulse (J) = Force (F)∆Time (t) Momentum (p) = Mass (m)∆Velocity (v) Therefore: J=p and F∆t=m∆v dividing by ∆t rearranges your equation to find force, giving you F=(m∆v)/∆t F=((1500kg)(13.41m/s-0m/s))/(.095s-0s) F=((1500kg)(13.41m/s))/(.095s) F=(20115kgm/s)/(.095s) F=211736.84N