In the figure here, a red car and a green car move toward each other in adjacent

Question

In the figure here, a red car and a green car move toward each other in adjacent lanes and parallel to an x axis. At time t = 0, the red car is atxr = 0 and the green car is at xg = 220 m. If the red car has a constant velocity of 27.0 km/h, the cars pass each other at x = 43.8 m. On the other hand, if the red car has a constant velocity of 54.0 km/h, they pass each other at x = 76.1 m. What are (a) the initial velocity (in km/h) and (b) the (constant) acceleration (in m/s2) of the green car? Include the signs.

Explanation / Answer

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 time t = 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 = 43.5 m, and if it has a constant velocity of +40 km/h, they pass each other at x = 77.3 m.
(a) What is the initial velocity of the green car?
(b) What is the acceleration of the green car?

one of the possible reasons you did wrong is you forgot to change to a same unit.

20 km/hr = 50/9 m/s

find the time when they pass each other
43.5 / (50/9) = 7.83 secs

red car = (50/9) (7.83)
green car = 0.5(a)(7.83)

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