# College Physics

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A red car and a green car, identical except for color, move toward each other in adjacent lanes and parallel to an x-axis. At time t=0, the red car is at x sub r = 0 and the green car is at x sub g = 220m. If the red car has a constant velocity of 20km/h, the cars pass each other at x = 44.5m, and if it has a constant velocity of 40 km/h, they pass each other at x=76.6m. What are (a) the initial velocity and (b) the constant acceleration of the green car?

• College Physics -

Use the two distances to calculate how long it takes then to pass each other.
For Vr = 20 km/h = 5.555 m/s, they pass after 44.5/5.555 = 8.01 seconds. At that time, the green car has traveled 220 - 44.5 = 175.5 m
For Vr = 40 km/h = 11.111 m/s, they pass after 76.6/11.111 = 6.894 s. at that time, the green car has traveled 220 - 76.6 = 143.4 m

Finally using those times and the corresponding distances traveled by the green car, solve two equations in two unknowns for Vo and a of the green car.

That step I leave up to you.

• College Physics -

Thanks a bunch!

• College Physics -

536

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