Homework Help: A question for all of u

1. Nov 6, 2005

emc2_akshay

Excuse me, but will anyone of u be kind enough to help me with this quetion----
Q.==== A truck is moving towards you with a velocity v. You throw a ball at it with velocity x, which bounces of elastically after hittin hthe truck. What is the speed of the ball now?:yuck:

2. Nov 6, 2005

Chi Meson

Since no masses are given, this is a conceptiual, not mathematical question. The answer is very simple if you understand a few concepts.

First there is an assumption: the mass of the truck is so much greater than the mass of the ball that the speed of the truck effectively does not change during the collision. So, that means you can "observe" this collision from the point of view of the truck (it's an "inertial reference frame). The elastic collision form the truck's POV, is just like the ball bouncing (perfectly elastically) off a stationary wall.

What is the incoming speed of the ball as seen by the truck? What is the outgoing speed of the ball as seen by the truck? Add to that last speed, the speed of the truck's frame of reference.

3. Nov 6, 2005

Fe-56

No, I really do not know to play such note