You are driving a car 35 mi/h down the road. The stoplight in front of you sudde

Question

You are driving a car 35 mi/h down the road. The stoplight in front of you suddenly turns red and you slam on the brakes, skidding to a halt. You get out of the car and measure the skid marks made by your tires to be 22.5 m meters. (Assume positive x to be in the forward direction)

Part A) What is the acceleration of the car in m/s^2 ?

Part B) If your car was going twice the velocity, how far would it take to stop if the acceleration were the same as for part A?

Part C) How long would it take the car to stop if it were going at twice the velocity?

Explanation / Answer

1 mi/h = 0.447 m/s

speed of the car = 35*0.447 = 15.645 m/sec

final speed = 0

displacement = 22.5 m

1) from the kinematic equation

v^2-u^2 = 2as

a = -u^2/2s = - 15.645^2/2*22.5

a = -5.44 m/s^2

2) if speed gets doubled

s = -u^2/2a

s = -31.29^2/2*(-5.44)

s = 89.99 m

3) v = u+at

t = -u/a

t = 31.29/5.44 = 5.75 sec

Related Questions

Navigate

• Browse (All)
• Browse Y
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.