A red car and a green car, identical except for the color, move toward each othe

Question

A red car and a green car, identical except for the color, move toward each other in adjacent lanes and parallel to an x axis. At timet = 0, the red car is at xr = 0 and the green car is at xg = 220 m. If the red car has a constant velocity of +20 km/h, the cars pass each other at x = 44.4 m, and if it has a constant velocity of +40 km/h, they pass each other at x = 77.9 m.

A red car and a green car, identical except for the color, move toward each other in adjacent lanes and parallel to an x axis. At timet = 0, the red car is at xr = 0 and the green car is at xg = 220 m. If the red car has a constant velocity of +20 km/h, the cars pass each other at x = 44.4 m, and if it has a constant velocity of +40 km/h, they pass each other at x = 77.9 m. What is the initial velocity of the green car? (Indicate direction with the sign of your answer.) What is the acceleration of the green car? (Indicate direction with the sign of your answer.)

Explanation / Answer

t1=44.4/(20*1000/3600)s=7.992s.

t2=77.9/(40*1000/3600)s=7.011s.

For 1st case:

44.4=Urel*t1 + 0.5a(rel)*t1^2 [Urel=Ured-Ugreen=100/18+Ugreen; a(rel)=a(red)-a(green)=a(green).]

44.4=(100/18+Ugreen)*t1 + 0.5a(rel)*t1^2. (1)

For 2nd case

77.9=U'rel*t2 + 0.5a(rel)*t2^2 [u'rel=200/18 + Ugreen]

77.9=(200/18 + Ugreen)*t2 + 0.5a(rel)*t2^2. (2)

Solving (1) & (2)

Ugreen=8.09m/s

a(green)=a(rel)=3.47m/s^2

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