# Ball size and bounce height

## Problem Scenario

This experiment will show comparisons that will determine if the size of the ball will affect the height of its bounce.

Does the size of a ball affect the height of its bounce?

## Specific Question

Comparing rubber balls of different sizes which one will bounce higher?

## Hypothesis

I think the larger ball will bounce higher.

## Graph of Hypothesis

Variables
Independent Variable: Size of a ball
Dependent Variable: Bounce height

### Variables That Need To Be Controlled:

height of drop, number of trials, ball air pressure, ball position from which to determine bounce height, consistent assistants.

## Vocabulary List That Needs Explanation

Air pressure:
Air pressure at sea level is the equivalent of having many blankets, which would feel very heavy. If you have only one blanket though, it would feel very light, and this is like the air pressure at the top of a mountain. Each layer of air presses down on the layers below, and so the greatest pressure is at ground level where we have the maximum amount of air above. If we go above the height of mountains and into the stratosphere, the pressure will decrease until it reaches about zero, as here there is hardly any air above it.
http://www.rcn27.dial.pipex.com/cloudsrus/pressure.html

## General Plan

Ensure all balls have the same air pressure using bike pump with gauge. Drop each ball from the same height 10 times and measure each bounce height. The balls will be measured each time with a tape measure.

Potential Problems And Solutions:
A ball might have less air in it, therefore ensure that all balls have the same air pressure prior to experiment. The ball may get damaged during the drops, so checking the balls for damage would determine if a new ball would be necessary. The assistants may witness different bounce heights due to perception, so assistants should agree which part of the ball to look at for height of bounce (bottom of the ball as it rebounds).

None

# Comparative Study

### Number Of Comparison Categories:

This experiment will compare the rebound height of three different sized sport balls.

### Number of Comparison Samples:

There will be ten different samples of rebounds for each size of ball.

### Number Of Observation In Each Sample:

The rebound height of each series of trials for each ball will be documented.

March 1, 2013

### Where will data be collected?:

Outside of the science room (B10) from the top of the second floor stairwell.

## Resources and Budget Table

 Item Number needed Where I will get this Cost A 1 own it \$0 B 2 own it \$0 C 3 Borrowed it \$0 D 4 own it \$0 E air pump Borrowed it \$0

## Detailed Procedure

Step 1: Set up the tape measure with centimeter-side up directly against the wall to measure the bounce height.
Step 2: Using an air pressure gauge, measure the air pressure of each ball.
Step 3: Determine the desired air pressure and inflate each ball to that level, testing air pressure at each interval.
Step 4: Using a flexible tape measure, determine circumference of each ball.
Step 5: Drop each ball one at a time from the top of the stairs from the exact same height (e.g. outstretched arms, shoulder height).
Step 6: Assistants record the height of each ball bounce.
Step 7: Drop each ball 10 times and record the heights.

## Photo List

All three balls together
Ball dropping
Measurement stick with the project

## Time Line

2/26/13 Do experiment
3/1/13 Experiment due
3/7/13 Analysis due
3/15/13 Discussion due
3/22/13 poster due
3/29/13 Science Fair

Data Analysis
The average bounce height for the smallest ball (58.7 cm) was 166.6 cm, which was a higher average bounce than both of the other larger balls. There was a smaller difference between the smallest ball and the medium-sized ball average bounce height (3.1 cm difference), than the difference between the medium ball and the largest ball average bounce height (10.7cm). The difference in circumference between the smallest ball and medium ball was 5.9 cm, whereas the difference in circumference between the medium and largest ball was 50.6 cm.

see data table

# Devon Russell's Ball Bounce Height Data

 Ball Bounce Trials 58.7 cm Ball Bounce Height (cm) 64.6 cm Ball Bounce Height (cm) 115.2cm Ball Bounce Height (cm) 1 161 168 145 2 182 177 181 3 162 167 138 4 162 155 145 5 165 162 152 6 174 162 155 7 163 159 157 8 167 161 149 9 165 162 152 10 165 162 154 Average Bounce Height (cm) 166.6 163.5 152.8

### Results

The larger ball (115.2 cm) average bounce height was 152.8 cm. The ratio of average bounce over size (152.8/115.2) was 1.326. The medium ball (64.6 cm) average bounce height was 163.5 cm. The ratio of average bounce over size (163.5/64.6) was 2.531. The smallest ball (58.7 cm) average bounce height was 166.6 cm. The ratio of average bounce over size (166.6/58.7) was 2.838.

### Conclusion

The experiment demonstrated that the size of a ball did affect the height of its bounce. The smaller the ball is, the higher it bounced.

## Discussion

If this type of experiment were to be repeated, there would be different types of balls with the same texture but in different format (e.g. solid rubber balls of different sizes versus basketballs of different sizes).

### Benefit to Community and/or Science

The people manufacture balls might be interested in the information about the different types of balls.

## Background Research

http://www.exploratorium.edu/sports/ball_bounces/ballbounces1.html

The experiment will use three different types of balls. The balls need to be the same texture.
The balls should be dropped two times during each trial. Their should be 3 trials for each ball

### References

http://www.exploratorium.edu/sports/ball_bounces/ballbounces1.html

### Abstract

This Science Fair project set out to answer whether the size of a ball affects the height of its bounce. My original Hypothesis was that the larger ball would bounce higher than a smaller ball.