# Homework Help: Physics Practical: Rebound height of a table-tennis ball

1. Aug 16, 2015

### Janiceleong26

1. The problem statement, all variables and given/known data

For part aiii), the mark scheme states "Use of set squares to indicate height". I know what are set squares, but how does it aid to determine the rebound height, h? I thought set squares are to ensure two objects are perpendicular to one another? How does it help in measuring the rebound height, h?

Also, for part c), how to explain? Is it because both h and d have the same unit, thus cancel out, giving a constant?

2. Aug 16, 2015

### BvU

Think of ways to ensure that you may measure h accurately along the ruler ....

In part c, apparently the theory has some relationship like $h^2 = e\; d^2$ (or some other power of length). What could is be related to ?

3. Aug 16, 2015

### Janiceleong26

By placing the set square like this? Why not use a ruler instead?

And I thought the theory is related by h = e^2 d? I really don't know what it is related to.. I guess it's Young's modulus?

Last edited: Aug 16, 2015
4. Aug 17, 2015

### BvU

That's the idea. You worry me because you let the top of the set square align with the center of the ball, whilst the h and d in the figure are measured with respect to the underside of the ball.

Young's modulus is too complicated in this experiment.
Think about the bouncing as a non fully elastic collision
At what speed does the ball hit the floor ?
How high does the ball bounce if the speed up is a fraction of that ?

Last edited: Aug 17, 2015
5. Aug 17, 2015

### Janiceleong26

Oh whoops sorry, was not conscious about it
But why can't we use other forms of straight edges, like a ruler instead of set squares?
I guess it's newton's law of restitution then?

6. Aug 17, 2015

7. Apr 6, 2017

### syedHa

Please mention from which year and session is this question from....TIA