You are driving your 1200 kg car down a straight section of highway at 35 m/s. Y

ID: 1647794 • Letter: Y

Question

You are driving your 1200 kg car down a straight section of highway at 35 m/s. You

encounter a sudden traffic jam, and the 5500 kg truck in front of you stops. When the truck is 120 m in

front of you, you slam on the brakes, and your car skids with a coefficient of kinetic friction of 0.25.

Your car hits the back of the truck and they stick together.

How far does do the car and truck travel together after the collision before stopping? (The

coefficient of kinetic friction between the road and the car+truck smashup is the same as it was for the

car.)

Deceleration after applying brakes = ug = 0.25g = 0.25*9.8

= 2.45 m/s^2

By third equation of motion,

v = sqrt (u^2 - 2as)

= sqrt (35^2 - 2*2.45*120)

= 25.24 m/s

Speed of car after sticking to truck

= (1200*25.24)/(5500+1200)

= 4.5206 m/s

Distance travelled before stopping = v^2 /2a

= 4.5206^2 /(2*2.45)

= 4.17 m answer

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