Physics Help In the figure below, a red car and a green car, identical except fo
ID: 1406655 • Letter: P
Question
Physics Help
In the figure below, 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 = 44.1 m, and if it has a constant velocity of 40 km/h, they pass each other at x = 75.6 m. (a) What is the initial velocity of the green car? (Indicate the direction with the sign of your answer. The positive direction is to the right.) (b) What is the acceleration of the green car? (Indicate the direction with the sign of your answer. The positive direction is to the right.)Explanation / Answer
use the conversion factor kmph = 5/18 m/s
so
20 kmph = 20* 5/18 = 5.56 m/s
time taken to pass each other, t = d/v = 44.1/5.56 = 7.93 secs
distance of red car = (5.56* 7.93) = 44.09 m
green car = 0.5(a)(7.93)² + 7.93V + 220
when the two car meets, they are in the same position,
(5.56) (7.93) = 0.5(a)(7.93)² + 7.93V + 220
given that if the red car travels at 40 kmph = (40*5/18) = 11.11 m/s, they'd pass each other at 77.3m
same process.
to find the time when they pass each other, t = 75.6/11.11 = 6.8s
red car = (6.8*11.11) = 75.6
green car = 0.5(a)(6.8)² + 6.8V + 220
(75.6 ) = 0.5(a)(6.8)² + 6.8V + 220
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so you have two equations:
44.1 = 0.5(a)(7.93)² + 7.83V + 220
75.6 = 0.5(a)(6.8)² + 6.8V + 220
1.03 V = -31.5 + 8.32a^2
solve for a and V and a
weget a = -4.71 m/s² and V = -4.45 m/s