# BOUNCE LAB

When a ball bounces on a surface such as the floor, it exhibits a behavior such that successive bounces occur closer and closer together in time, and the height of successive bounces grows smaller and smaller. This same pattern can be seen when a laboratory cart equipped with a spring plunger rolls down an inclined plane and collides with a fixed barrier, or when an air track glider on an incline strikes an elastic barrier.

Four questions come to mind during any of these occurrences, and these furnish the purpose for this lab.

## Purpose

A) What is the mathematical pattern for the motion of your object during any one bounce? How do various constants relate to the motion of your object?

B) What is the mathematical relationship which matches the heights of the bounces of your object?

C) What is the mathematical relationship which matches the times for subsequent bounces?

D) How are the times for the bounces related to the heights of the bounces?

## Procedure

1. Drop your ball, roll your cart down the incline, or slide your glider down the airtrack. Record position vs time for multiple bounces (5-8) of the object. Repeat as needed until you get a smooth set of data.

2. Carry out the analysis called for in (A) above.

3. Carry out the analysis called for in (B), (C) or (D) above, as directed for your group.

4. Repeat the experiment, varying either the ball, the surface onto which the ball is dropped, the angle of the incline, or the mass of the cart (glider) as is appropriate for your group.

## Experimental Specifics

 Group Experiment Description Equipment Setup 1 2 3 You will release a ball from a position near the floor, table top, etc. Track its motion as it bounces off the surface. 1 = A & B 2 = A & C 3 = A & D Ball Motion Detector Interface CPU w/ Software * 4 5 6 You will release a lab cart from a position near the top of an inclined plane. Track its motion as it bounces off of a fixed object at the bottom. 4 = A & C 5 = A & D 6 = A & B Lab Cart Inclined Track Motion Detector Interface CPU w/ Software * 7 8 You will release an air track glider from a position near the top of an inclined track. Graph its motion as it bounces off of a fixed elastic object at the bottom. 7 = A & B 8 = A & C Glider Air Track Elastic Bumper Motion Detector Interface CPU w/ Software *
* CPU w/ Software = Computer, LabQuest, Calculator or Palm OS Device plus appropriate data collection software

Clarence Bakken
Updated 11/11/07