Question

A car is traveling at 50km/h. The driver sees a child run out into the road 5m ahead. She applies the breaks and the car stops in 5s. The driver's thinking time is 1.5s.
a. Will the car stop in time?
b. If the driver's thinking time is increased to 2.5s, will the car stop in time?
c. What happens if the thinking time is 1.5s but the car is traveling at 64km/h?

Answer 1

Are you sure the child is only 5 m ahead?
Vo = 50km/h = 50,000m/3600s = 13.89 m/s.

a. V = Vo + a*t = 0.
13.89 + a*5 = 0, a = -2.80 m/s^2.
V^2 = Vo^2 + 2a*d.
V = 0, Vo = 13.89 m/s, a = -2.80m/s^2, d = ?.

b.

Answer 2

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Answer 3

Initial u=14m/s a=-2.8m/s^2 s=5 the time needed to stop can be find 5m=14t-2.8t^2÷2

Answer 4

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Answer 5

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Answer 6

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