Question

A truck with mass 3000 kg is driving at 20 m/s north. It collides with a car of mass 1200 kg traveling east towards the truck at 30 m/s. How fast, and in what direction, will the two be traveling after the collision if it is perfectly inelastic?

	a.	16.7 m/s at 31 degrees north of east.
	b.	16.7 m/s at 59 degrees north of east.
	c.	36.1 m/s at 33.7 degrees north of east.
	d.	50 m/s Northeast.

Answer 1

Let the North is along the positive x-axis while East is along positive y-axis. The initial momentum of truck and car was

After the collision, which is perfectly inelastic, both the truck and car will stick to each other hence the mass become . Let the final velocity of the combine mass will be then using conservation of momentum, we have

Magnitude will be

direction will be (with respect to x-axis or north)

Ans (b)