Two cars collide at an intersection. Car A , with a mass of 1800kg , is going fr

Question

Two cars collide at an intersection. Car A, with a mass of 1800kg , is going from west to east, while car B , of mass 1500kg , is going from north to south at 15m/s . As a result of this collision, the two cars become enmeshed and move as one afterwards. In your role as an expert witness, you inspect the scene and determine that, after the collision, the enmeshed cars moved at an angle of 55? south of east from the point of impact.

Part A) How fast were the enmeshed cars moving just after the collision?

Express your answer using two significant figures. (I tried 8.75 but it said it was wrong and I only have two more tries please help!)

Part B) How fast was car A going just before the collision?

Express your answer using two significant figures.

Explanation / Answer

add the momentum vectors.

A has a momentum Pa = 1800*Va angle 0
B has a momentum Pb = 1500*15 angle -90 = 22500 angle -90
R has momentum R = R angle -55

Ax = 1800*Va
Bx = 0
Rx = Rcos(-55)
Ay = 0
By = -22500
Ry = Rsin(-55)

summing x and y
1800*Va = Rcos(-55)
-22500 = Rsin(-55)

from the last, R = 27467.43
1800*Va = Rcos(-55)
1800*Va = 27467.43 cos(-65)
Va = 6.45 m/s (b)

total mass is 3300 kg, so if total momentum (R) is 27467.43, then
Vr = 27467.43/3300 = 8.32 m/s (a)

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