A car sits on an entrance ramp to a freeway, waiting for a break in the traffic.

Question

A car sits on an entrance ramp to a freeway, waiting for a break in the traffic. Then the driver accelerates with constant acceleration along the ramp and onto the freeway. The car starts from rest, moves in a straight line, and has a speed of 20 m/s (45 mi/h) when it reaches the end of the 120-m-long ramp, (a) What is the acceleration of the car? (b) How much time does it take the car to travel the length of the ramp? (c) The traffic on the freeway is moving at a constant speed of 20 m/s. What distance does the traffic travel while the car is moving the length of the ramp?

Explanation / Answer

a) let acceleration be a

by the equation

V2 = U2 + 2as

since u=0

a = V2/2s = 202/2*120 = 400/240 = 1.66 m/s2

b) time taken to travel is

t = V/a = 20/1.66 = 12 seconds

in that time traffic will travel s = 12*20 = 240 meters

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