# Physics

posted by Dani

A car is stationary at a stop sign when it is hit directly from behind by a truck of mass 3000kg which was travelling at a speed of 9 m/s immediately before the collision. The two vehicles lock together and move forward with an initial speed of 6 m/s.
a) what is the mass of the car?

b) If the car had been designed with a crumple zone, explain in correct physics term, why this might reduce the risk of injury to the driver.

1. Damon

initial momentum = 3000*9

final momentum = (3000+m)*6

final momentum = initial momentum
solve for m

b) F = m a
If a is less force is less.
a is rate of change of velocity
if velocity change is spread out over a longer time, a is less and F is less.

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