# Ball down a ramp projectile.

• bwagner

## Homework Statement

A ball is placed 0.700m from the end of a declining ramp and rolls down the ramp in 0.750s. The marble is also 0.175m from the horizontal. The ball hits a mark on the floor that is 1.70m from the bottom of the ramp on the x-axis. What mount of time is the ball in the air after leaving the ramp?

## The Attempt at a Solution

Can't find initial velocity.

Seems like a couple of approaches are available: one is to simply find the average velocity from the length of the ramp anf the time spent. Since acceleration is uniform the velocity as it leaves the ramp is twice that (initial velocity is zero).

The other is to equate potantial energy loss with kinetic energy gain while on the ramp.

In other words, mgh=1/2mv^2

From there you need to know the angle of the ramp. Then resolve the velocity in the x direction. This help?

The velocity,as it leaves the ramp, is twice what? The calculated velocity of distance/time?

Yep. The reason is that the acceleration is uniform. Otherwise this isn't true.