# Homework Help: Energy Loss of a ball falling off the lip of a ramp

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1. Mar 20, 2016

1. The problem statement, all variables and given/known data
This is a Lab:
A Ball is placed on a 14cm high ramp and it rolls down to the bottom of the ramp and onto a table where it rolls 20cm (the ramp's horizontal displacement is 16.5cm). After rolling on the table, the ball falls off the table for 76.5cm with a forward horizontal velocity. The goal of the lab is to predict where the ball will land on the ground. **There is also a 1cm drop between the ramp and the table (this is the problem)
2. Relevant equations
Ug=mgh, KE=0.5m(v^2), Basic Kinematic Equations

3. My question:
I have attempted this lab by assuming that the gravitational potential energy is completely converted over into kinetic energy, so I set their equations equal in order to find velocity. My teacher has informed us that since the ball we use is metal, frictional force between the ball and table is negligible. With this information, I can assume that the velocity of the ball coming off of the ramp is equal to the velocity of the ball when exiting the table. I then predict the landing point by using kinematics, however, i always predict it too far. I believe this is because there is a 1cm drop between the ramp and the table that causes the ball to bounce and lose energy. How can I calculate this energy loss?

2. Mar 20, 2016

### Staff: Mentor

Did you take any notes on the amount of bouncing you observed? How long did it take for the ball to resume smooth horizontal motion?

Maybe look for other places the energy could go first? When the ball moved down the ramp did it roll without slipping or did it slide without rolling? Maybe a combination of both, some slipping before rolling?

3. Mar 20, 2016

### haruspex

Velocity is a vector. Those two directions are different so the velocity cannot be the same. But the speeds will not be the same either. What will be (more or less) the same?

4. Mar 21, 2016

Ok, these are good considerations, thank you!

5. Mar 21, 2016

### haruspex

Please respond to post #3, or at least clarify what you meant by saying the velocities would be the same.

6. Mar 21, 2016

I meant to say that there would be a constant horizontal velocity from the exit point of the ramp to the end of the table, since there was no friction

7. Mar 21, 2016

### haruspex

Ok.
You mentioned a 1cm drop at the end of the ramp. Are you counting that in the GPE that gets turned into KE?
Are you taking into account the rotational KE?
What friction there is from the table should send it further. When it drops from the ramp, its rotation should be too fast for its horizontal velocity, so any friction will turn some of the rotational KE back into horizontal KE.