Kinematics Problem.

1. Sep 24, 2004

hi guyes, I was wondering if someone could help me with a problem I had on a quiz. The question hes been puzzeling me for some time now.

A ball is thrown upward in an open roof elevator travelling at 10m/s(elevator speed). The balls speed is 20m/s. How much time does it take for the ball to reach the same point it was thrown at?

2. Sep 24, 2004

Pyrrhus

You could use galilean transformations to solve this one, the 10m/s of the elevator must be relative to a inertial frame observer, as the 20m/s. Find the speed relative to the elevator, to simplify calculations.

3. Sep 24, 2004

Staff: Mentor

Is the elevator rising or falling?
I assume that's the ball's speed with respect to the earth/elevator shaft.
I assume you mean same point with respect to the elevator car?

Find the position of the elevator car as a function of time. (Constant speed.)
Find the position of the ball as a function of time. (Constant acceleration.)

Set them equal and solve for the time.