Question

A car's bumper is designed to withstand a 5.04-km/h (1.4-m/s) collision with an immovable object without damage to the body of the car. The bumper cushions the shock by absorbing the force over a distance. Calculate the magnitude of the average force on a bumper that collapses 0.255 m while bringing a 890-kg car to rest from an initial speed of 1.4 m/s.

Answer 1

3420.39 N

Step-by-step explanation:

Applying,

Fd = 1/2(mv²-mu²)................. Equation 1

Where F = force on the bumber, d = distance, m = mass of the car, v = final velocity, u = initial velocity.

make F the subject of the equation

F = (mv²-mu²)/2d............... Equation 2

From the question,

Given: m = 890 kg, v = 0 m/s (to rest), u = 1.4 m/s, d = 0.255 m

Substitute these values into equation 2

F = [(890×0²)-(890×1.4²)]/(2×0.255)

F = -1744.4/0.51

F = -3420.39 N

The negative sign denotes that the force in opposite direction to the motion of the car.