* Velocity is the distance travelled in a stated direction (in this case down) or displacement divided by time taken;
Velocity = Displacement
Time taken
So if we use the example:
Displacement= 2
Time taken = 0.5 …the velocity would be 4.
So the Kinetic energy of a squash ball being dropped from 2 metres, with a velocity of 4 would have a kinetic energy of:
½ x 0.237 x 16 = 1.896j
There will also be a resisting force (air resistance) acting on the ball, but as the investigation doesn’t require the ball to reach its terminal velocity there will be very little of it, so this will have minimal effect on the results. Another factor which will effect the accuracy of the results is that every time the ball is dropped, it gets slightly warmer which, because of the increased potential energy, may result in the squash ball bouncing higher.
Method
The experiment is going to show how much energy is transferred when the squash ball is dropped. This will be done by dropping the squash ball from five different heights and recording the height bounced. The amount of energy transferred will then be worked out by: -
- Working out the squash balls GPE in relation to the height it was dropped from
- Subtracting from the GPE the MGH (mass x gravity x height) of the height to which it bounced, for example
Balls GPE= 0.237 x 10 x 2= 4.74
MGH of height bounced= 0.237 x 10 x 0.54=1.2798
So the energy transferred would be:
So 3.4602j of energy has been transferred into heat and sound.
As I am using two different squash balls (one with a white spot and one with a red spot) I will repeat this process on both sets of results for the five different heights.
Prediction
I predict that as the balls dropping height increases; the energy transferred will also increase
Conclusion
From my results I can conclude that as the temperature of the ball rises the height of the bounce gets higher. This is in line with the kinetic theory, which defines that as the ball gets hotter the atoms get more energy and vibrate more. When the ball hits the surface then the atoms are pushed together and because they are vibrating more they push each other further away causing the ball to bounce higher. In this experiment the kinetic theory only lasts for a specific set of temperatures. This is because when the ball hits a certain temperature it starts to melt. At 0 degrees Celsius the ball will still bounce as the atoms are still vibrating. The graph proves that the theory works for this experiment, as it is a straight line to start with. However as the ball gets nearer the critical temperature the extra height it bounces becomes less and less. This is shown as the graph levels off. The sketch graph I drew in my prediction matched the real graph showing that the science I used to explain my prediction was correct.
Evaluation
Looking at my results I can say that they were quite reliable and accurate. I had one anomalous result even after an average over five measurements. I can say that looking at my results when I repeated results they were quite close together. I think that I did the experiment quite well although I found it hard to spot where the ball bounced too. This is why I did an average over 5 measurements. To improve the experiment I would need to use specialist equipment like lasers so I could be sure where the ball bounced too. Ways in which I could extend this experiment are to use a different kind of rubber in the ball so that it doesn't melt at such a low temperature this way I could carry on to see whether the kinetic theory is still right at higher temperatures. Also I would like to see what happened when the ball was at 0 degrees Celsius. I would like to do this to see whether the atoms still vibrated causing the ball to bounce. If it did I would like to carry on getting lower and lower to see whether there was a temperature where the atoms no longer vibrated (Absolute Zero)
