# Investigating the Percentage Energy Loss When a Ball Bounces

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Introduction

## Eva Elks – 11M

Investigating the percentage energy loss when a ball bounces

Theory:

When an object is lifted up, work is done. Once the object is in the raised position, it has gravitational potential energy. The energy it is has is the same as the work done to get there. When the ball is lifted to the height it will be dropped from it will, therefore, gain gravitational potential energy. This means that when my ball is in the raised position it will have gravitational potential energy. The equation for this is:

## Potential energy = Mass x gravity x height

When the ball is dropped this is converted into kinetic energy. The equation for this is:

## Kinetic Energy = ½ x mass x velocity2

However, the energy transfer is not perfect. Some of the energy will be wasted as non-useful energy, mainly heat and sound. This means that when the ball bounces upwards again, it will not have as much energy as when it was dropped and will therefore not bounce up to the same height.

Middle

The size of the balls will effect my results because Force=Pressure x Area so a change in area would also cause a change in force.

The temperature of the ball will effect my results because if there is a higher temperature then the molecules will move at a greater speed and the ball will have more energy causing it to bounce higher.

The surface I drop my ball onto will effect the amount of energy lost because some surfaces, like softer surface, will absorb more energy and cause the ball not to bounce up as high.

To ensure a fair test I will choose one variable to change, and keep the others constant throughout the investigation. There are other variables that could effect the outcome of my investigation, for example gravity. However, gravity is always constant on the earth, and is a force of about 9.8m/s2. This would be too hard for me to change in a classroom situation. I will

Conclusion

I will try and drop the balls straight downwards because this will make it easier when I measure the height they bounce up to, as I wont have to move the ruler too much. This will also ensure a fair test, as my results will be more accurate if I am not moving the meter rule, as moving it could mean it is not entirely straight and would cause me to take an inaccurate measurement.

I will not exert any force on the balls as I drop then, because it would be virtually impossible to keep the force constant, and would therefore make my results unreliable.

I will calculate how much energy my balls have using the equation PE = mgh,this will be PE1. I will then drop my ball and record the height it bounces up to. I will then record its potential energy, again using the formula PE = mgh, this will be PE2.

I will then find the percentage of energy they have lost using the formula:

PE2 x 100

### PE1

Diagram:

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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