Question

A car heading north collides at an intersection with a truck of the same mass as the car heading east. If they lock together and travel at 28 m/s at 37° north of east just after the collision, how fast was the car initially traveling? Assume that any other unbalanced forces are negligible.
what is the correct answer
34 m/s
17 m/s
26 m/s
68 m/s
...?

Answer 1

This phenomenon is an inelastic collision. The problem is easier to solve because the masses of the colliding bodies are equal. By conservation of momentum, the final momentum of the bodies as one is equal to the VECTOR sum of the momentum of individual bodies. 

For this problem, the final velocity of the two cars is the sum of the initial velocities of each car. The velocity of the car is just the component of the velocity along the north direction.

Using trigonometry,
v1 = vf * sin(theta)
v1 = 28 * sin(37)

v1 = 16.9 m/s