# DYNAMICS

A car has an initial speed of 25m/s and a constant deceleration of 3m/s^2. Determine thewvelocity of the car when t=4s. What is the displacement of the car during the 4-s time interval? How much time is needed to stop the car?

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1. v = Vi + a t
v = 25 - 3 t
v = 25 - 3(4)
v = 13 m/s after 4 sec
average speed during the 4 s = (25+13)/2 = 19 m/s
so distance = 19*4 = 76 meters

0 = 25 - 3 t
t = 8 1/3 seconds

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2. Good

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