Two cars collide at an intersection. Car A , with a mass of 1900kg , is going fr

Question

Two cars collide at an intersection. Car A, with a mass of 1900kg , is going from west to east, while car B, of mass 1500kg , is going from north to south at 12.0m/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 55.0? south of east from the point of impact.

How fast were the enmeshed cars moving just after the collision?

How fast was car A going just before the collision?

Explanation / Answer

For Car A:
p=mv
p=1900*u Ns (use u as velocity so there is no confusion later on)

For Car B:
p=mv
p=1500*15
p=22500 Ns

For Enmeshed Cars:
m=1500+1900
m=3400kg

p=mv
p=3400*v Ns

Resolve Vectors:
theta=65 degrees

Adjacent=1900*u Opposite=18000   Hypotenuse=3400*v

A)
sin(theta)=O/H
sin(55)=18000/(3400*v)
v=18000/(3400*sin(55))
v=6.46m/s (2 sig figs)

The enmeshed cars are moving at 6.46m/s.

B)
tan(theta)=O/A
tan(55)=18000/(1900*u)
u=18000/(1900*tan(55))
u=6.63m/s (2 sig figs)

Car A is moving at 6.63m/s, just before the collision.

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