A set of crash tests consists of running a test car moving at a speed of 10.4 m/

Question

A set of crash tests consists of running a test car moving at a speed of 10.4 m/s (23.3 mi/hr) into a solid wall. Strapped securely in an advanced seat belt system, a 61.0 kg (135 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.
b) Using the direction of motion as the positive direction, calculate the average acceleration of the dummy during that time (in g's, with 1g = 9.81m/s2)

Explanation / Answer

v^2 = u^2 + 2as

a = -g

v = 0

u = 10.4

0^2 = 10.4^2 - 2*a*0.84

s = 10.4^2/(2*0.84) = 64.38 m/sec^2

F = ma

F = 61*64.38 = 3927.18 N

B.

a = (64.38/9.81)*g = 6.56 g

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