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While driving your car (total mass 1600 kg) on a level (horizontal) road, you ap

ID: 1619090 • Letter: W

Question

While driving your car (total mass 1600 kg) on a level (horizontal) road, you approach a red light. (Your car faces in the +x-direction and moves only along the x-axis.) At the moment you start braking (t = 0), your initial position is x = 0 and your initial velocity is 14 m/s. You decelerate at a constant -4.5 m/s^2 until your car comes to rest. 5. What distance does your car travel while braking? A. 19 m B. 22 m C. 25 m D. 28 m E. 31 m 6. What net horizontal force (x-component) acts on your car while braking? A. -3500 N B. -4400 N C. -5300 N D. -6200 N E. -7200 N 7. Which one of the following graphs best represents the car's velocity as a function of time? 8. Which one of the following graphs best represents the car's position as a function of time? During your car's deceleration, a physics book on your level (horizontal) passenger seat stays in the same place, without sliding. The physics book has unknown mass. What is the minimum value of the coefficient of static friction between the book and the seat? A. 0.46 B. 0.52 C. 0.58 D. 0.64 E. 0.71

Explanation / Answer

5.

a = deceleration = - 4.5 m/s2

Vo = 14 m/s

Vf = final velocity = 0 m/s

d = stopping distance

using the equation

Vf2 = Vo2 + 2 a d

02 = 142 + 2 (-4.5) d

d = 21.8 m

d = 22 m

6

F = ma = (1600) (- 4.5) = - 7200 N

7.

E