Preliminary work: Before my experiment I did some smaller experiments. I experimented with different surfaces. Here is a table of my findings (using averages)
I found that the floor gave the best results, its also solid and easy for angle of interception and for getting results from.
I also tested different types of balls to find how well they bounced; I wanted a middle bouncing power of ball so that the results are easy to gather.
The ping-pong ball had a lot of variation while the tennis ball did not; from this I think I will use the tennis ball for my experiment.
The Experiment
Apparatus: You will need a measuring stick of 1 metre in length, a tennis ball and someone to help and a few pieces of cello tape.
Diagram:
Safety: Do not throw tennis balls at other, these can cause injuries, also watch out for balls on the floor because you my slip on them and fall. All obstacles need to be moved encase of accidents, you can fall over these.
Method: Here are the instructions you need to follow to do this experiment.
- Stick the ruler directly to the wall vertically with the 0cm end touching the floor.
- Get the other person to drop the ball at 10 cm (when this is the top of the ball), watch for the ball bouncing and measure from the top of the ball the height to the nearest ½ centre meter, this is because you will not be truthfully accurate otherwise, human vision is not good enough.
- Repeat this 4 more times at the same height so that after you can work out an average for the height.
- Do the same every 10 cm
- Put all results into a results table like this one.
Results: Here is a table of my results
Graph:
Conclusion
My graph shows there are trends that as the height the ball is dropped from increases so dose the bounce height. This shows that as the gravitational potential energy the ball has before it is dropped is converted into kinetic energy while the ball is falling, this increases as the height increases because the gravitational pull alters slightly and the ball is dropping for longer so kinetic energy builds up more and then into elastic potential energy as the force from the ground does work on the ball.
These show the same as I predicted, this was that as the height increase that the bounce height will increase as well. So far I managed to prove that my theory that the kinetic energy as the ball falls would increase with height the ball is dropped from, so that the more height there is the higher the rebound will be.
Evaluation
I found my results were all evenly spread out at about the same distances with no irregular results. There tended to be a pattern:
Height from which the ball was dropped divided by 10; timed by 6, add 6
This worded only 1 or 2 cm out for all averages but for the first result that was the same but without adding six on at the end.
There don’t seam to be any strange results, the furthest out from my line of best fit are my results for 10cm, 30cm and 90cm but these are not far out. I think this could be because the results were taken by human eye, so they may have errors and with the speed of the movement of the ball, it was nearly impossible to workout the exact height the ball managed. This could have been done better if a set infa-red sensors had of been used, this would have been so that the ball would break the rays and the last one broke was the height the ball reached. This would give much more accurate results that could be to 1mm or less. This would also help more with trends and averages.
There were other problems with the plan. The person who was meant to drop the ball from certain heights may have got some wrong be a small distance that would affect results; this may have been why I had those three odd results. This means the results may not be good enough to make a solid conclusion and it would be better to do the experiment again and drop the ball more accurate more times, dropping the ball more times would help make the results more reliable. I could also try dropping the ball from more heights, may be some larger ones and some in between ones like 150 cm and 45cm.
I now could get more relevant information on the Internet to find out what information there is on this area that could help my experiment. I could also do another experiment changing the heights I use and doing more drops at the same point for more accurate results to see if the same patterns appear. I could attempt to do the whole experiment again at a new temperature and see is the same trends appear still to help on going research how bouncing balls are effect and what stays the same what ever.
I think the experiment went well with good results and no major problems.
