Question

A set of crash tests consists of running a test car moving at a speed of 11.4 m/s (25.08 m/h) into a solid wall. Strapped securely in an advanced seat belt system, a 55 kg (121 lbs) dummy is found to move a distance of 0.78 m from the moment the car touches the wall to the time the car is stopped. Calculate the size of the average force which acts on the dummy during that time.

Answer 1

4582 N

Step-by-step explanation:

The initial speed of the test car is

u = 11.4 m/s

While the final speed is

v = 0

The displacement of the test car during the collision is

d = 0.78 m

So we can find the acceleration of the car by using the following SUVAT equation:

`v^2 - u^2 = 2ad\\a=(v^2-u^2)/(2d)=(0-(11.4)^2)/(2(0.78))=-83.3 m/s^2`

Now we can find the average force acting on the dummy by using Newton's second law:

F = ma

Where m = 55 kg is the mass. Substituting,

`F=(55 kg)(-83.3 m/s^2)=-4582 N`

So the size of the average force is 4582 N.