Question

In a front-end collision, a 1400 kg car that has shock-absorbing bumpers can only withstand a maximum force of 75 kN before any sort of damage occurs.If the maximum speed for a car that is nondamaged in a collision is 10 Km/h, by how much must the bumper be able to move relative to the car?

I got 0.068 meters, where did i go wrong?

Answer 1

The work done as the bumper is compressed the maximum distance with no damage, which is Fmax*X/2, must exceed the kinetic energy of the car. (The factor of 1/2 comes in because the force increases linearly with compression.)
X = [2/Fmax)]*(1/2)*M*Vmax^2
X = M*Vmax^2/Fmax

Convert 10 km/h to ? m/s before using the formula.

I get 0.144 meters. Your error may be in the factor of 1/2

Answer 2

Unless specified, linear compression probably has no bearing on the problem.

.5mV^2 = F*D is the correct formula.

10 kpm = 2.77 m/s

0.072 is the best answer.