A set of crash tests consists of running a test car moving at a speed of 13.0 m/

Question

A set of crash tests consists of running a test car moving at a speed of 13.0 m/s (28.6 m/h) into a solid wall. Strapped securely in an advanced seat belt system, a 69.0 kg (151.8 lbs) dummy is found to move a distance of 0.840 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.

A) Using the direction of motion as positive direction, calculate the average acceleration of the dummy during that time (in g's) (use 1g=9.8 m/s2).

Use Newton's second law. What should the sign of the answer be? The dummy is being slowed down, so the acceleration is - since the dummy is moving in the + direction.

Please help! The answer is not 100.59.

Use Newton's second law. What should the sign of the answer be? The dummy is being slowed down, so the acceleration is - since the dummy is moving in the + direction.

Please help! The answer is not 100.59.

Explanation / Answer

v^2 = u^2 - 2as
=>0 = (13)^2 - 2 x a x 0.84
=>a = 167.32 m/s^2
=>By F = ma
=>F = 69 x 167.32
=>F = 11545.08 N

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