For this we would measure the ball each time we dropped it and changed the temperature for each experiment to show how temperature affected the efficiency of the bounce.
Out of all these factors we chose the to alter the height at which we dropped the ball from. This was because it was the most simple to do and get right without having too many anomalous results.
Decision and Prediction
I have decided for my investigation on what affects the efficiency of a bounce of a ball to change the height at which the ball is dropped from each time and then collect the data. I will not change any other factors for example temperature of the ball or surface, the texture of the ball i.e. rubber, plastic. I will also make sure both the ball and surface are not damaged after each experiment.
My prediction is that at each height the ball is dropped from, it will behave in the same way, lose some energy and will reach about ¾ proportionally of the height at which it is dropped. This is because if it is dropped on the same surface and has the same mass it should not change its behavior whilst dropping.
Fair test
To ensure that when we did the experiment we had a fair result, we needed to address some issues. Here are some we needed to consider when conducting the test.
- The temperature of the ball. Make sure the temperature of the ball stays the same each time it is dropped as this could affect the weight and shape of the ball which would create anomalous results
- The temperature of the surface.
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Ensuring the ball is dropped not thrown.
- Making sure air resistance does not affect the result (this would probably only be an issue if we were dropping from much larger heights)
- Ensure no damage to the ball after being thrown
We tried to make sure that each set of experiments were set out and followed through carefully and preferably with the same apparatus. We eliminated certain variables by using a clamp stand to drop the ball instead of a human hand. We also made sure the surfaces were equal.
Safety
Safety is always very important whilst carrying out an experiment. Fellow students were using; Bunsen burners, scissors and these are even greater hazards when balls are concerned.
Here are some safety precautions we had to take whilst carrying out our experiment.
- Always tie hair back.
- Always wear an overall.
- Make sure you Bunsen burner is on a safe flame.
- Don’t throw the balls around unnecessarily.
- Wear goggles whenever experiment is taking place around you.
- Be careful with thermometers.
The Preliminary experiment
In the preliminary experiment we carried out, we did the experiment under the same conditions as we would in the real thing. Our prediction seemed right as the readings almost made a straight diagonal line once on a graph.
Method
We used two-meter rules and stuck them up on a wall ready to measure, and then we used a clamp-stand to hold the ball steady at a certain height ready to be released. We started at 20cm and then progressed by 0.2m every time until reaching 2m. We did not drop the ball by hand because this would not be avoiding variables like, temperature and height.
The Actual results
To discover the efficiency of the bounce we used the equation
Efficiency = Energy after bounce
Energy before bounce
And the energy was calculated by using this.
Change inP. E = weight change in height
For example for the first result in the above table I did these calculations
Change in P, E =
Conclusion
I was very pleased with my results as they showed a linear relationship and there was hardly any fluctuation on the graph. I believe this to be because a ball will always behave in the same way from whatever height it is dropped from. In affect it will bounce to proportionally ¾ of the original height. If this pattern reoccurs consistently then a straight diagonal line will be achieved so as we were only off by mm s each time, I believe we achieved our objective. There were no anomalous results in our experiment. I believe this to be because, although we did not follow all the criteria we could have done, we stuck to the main factors in our fair test and only ignored some of the second order affects. I believe that ignoring the second order affects was the cause of the slight inaccuracies on the graphs.
Evaluation
After finishing the experiment and completing the results table I found that the final results were very similar to my prediction. I predicted that the height of the bounce of the ball would be around ¾ proportionally of the original height unless made heavier or hotter. This is because on the graph there was a linear relationship and the ball behaved the same even at different heights. The things that would affect this would:
- The temperature of the ball. If the gas heated up in the ball then it would expand slightly which would make it less streamline. It would also get harder, also affecting the way it impacted the floor.
- The temperature would maybe affect the rubber lining causing it to soften and maybe damage more on impact.
These are all second order affects but if I did this experiment again I would definitely record the temperature before and after because there is a slight chance it could go up, thus affecting the next result.
Another thing that could change the speed of the ball and in effect, the efficiency of the bounce, is air resistance. This would only be an issue if there was a higher velocity and the objects were not streamlined. We could also create this affect by dropping the ball in a vacuum.
