This was incorrect, as 12. 3 x 2 does not equal 20. 407. I believe this was because in this case air resistance did have an affect, or the heat I expected to transfer from my hand did not, maybe due to it me doing the experiment in the middle of winter. On the other hand, in my prediction I stated that the bounce height would increase as the drop height increases, and the straight line defiantly shows this. In my opinion, at the end of the graph, the gradient increases causing a steeper end to the graph.
This is probably because I did these heights at the end of the experiment, therefore the ball will have had time to warm up, causing the molecules inside to move around and make the outer edge of the ball harder, meaning it bounces higher. I believe that my graph does not have a very steep gradient due to that when I drop the ball higher; the friction against the air coincidently increased. I decided to draw my graph from the origin point, as that is the only point of the graph that is free of experimental error, as you can’t drop a ball from nothing and expect it to bounce, as it has no GPE.
Evaluation: Overall, I do not think this experiment was very reliable, as there were so many factors that were out of my control to manage. These were such things as the air temperature, the air resistance, heat, and the pressure inside the ball. The air temperature could have affected the activity of the molecules inside the ball, and brought into action the Kinetic theory. The kinetic theory is that of the molecules gaining more energy and exerting it on moving around, consequently colliding with each other and making the ball harder due to the increase in the pressure.
This may have made the ball bounce harder as it got hotter through the experiment. Although I said pressure would be one of my controls, I did not take into account the pressure building up due to the heat transferred. Moreover, I could not control the air resistance, although this should have stayed constant, I can’t be sure. If the air temperature increased through the experiment, maybe because of the body heat given off, it would mean that the air resistance increased. This is because the heat gives the molecules energy, so the ball would have to use more energy to push past them.
This energy is then lost, and means that the ball does not have as much energy as it would if it were cooler. Furthermore, I think because we used our eyesight to determine the height of the re-bounce, this made our results even more unreliable. Yet, on-the-other-hand, I also think my results were as reliable as could I could get them. This is due to the limited time and equipment. For instance, because we used a clamp and stand to hold up the ruler, it made the results trustworthier than someone holding it up.
Also, the only thing we varied was the height we dropped the ball, everything else was kept exactly the same, for example, the ball we used, and the surface we worked on. What’s more, I followed the procedure correctly and missed nothing out. I measured the height of the re-bounce from the bottom of the ball instead of the top, as when we dropped it the bottom was inline with the top of the ruler. Moreover, because I got an average, it reduced the affect of anomalous results, which meant my result are unlikely to be flawed due to me as the dropper.
I do not think the way I measured the height was very accurate, as it depends on individual eyesight, and everyone’s level of eyesight is different. Although, they way I dropped the ball, and how we went about trying to record the closest measurement was accurate. This is because I used only my finger and thumb to hold the ball, this was to pass as little heat over as possible, and stop dropping the ball with an added force. I believe this worked, as on my graph there are no obvious anomalies, the line is not straight, but that is due to only a small bit of experimental error.
If I repeated the experiment there would be lots of things that I would do differently. I would conduct the experiment on the floor instead of on the bench, as maybe the increase G. P. E on the bench influenced my results. Also, I would find some way of controlling the air temperature, and the air resistance, although this would have to be done outside of the lab. I think that the temperature and the air resistance did have an effect on my results as the percentage of energy lost increased as I dropped the ball from higher positions.
Moreover, I would find a way to measure the level of the re-bounce that would be more dependable than using my own eyesight. This is because, as I have said, eyesight is not consistent as things such as the light intensity, which may affect the recording of the results, can influence it. Furthermore, I would increase my drop heights to 200cm, as I think if I carried on longer, my graph would show a definite point where terminal velocity came into action, and also that that graph would perhaps increase its gradient as the ball got hotter through the experiment.
This would be useful as it would mean my results could be analysed further and draw a conclusion more valid. Although, if I did do the investigation again, I would keep the squash ball in my experiments. I believe it gave reliable results subject to the terms and conditions that applied freely. Also, I would use the same unit of measurements, as they showed the results clearly and were more appropriate than other methods.
I could repeat the experiment under converse conditions by for instance changing the surface, or the air temperature. I could also vary the ball I used, as this would allow me to compare different bounce heights from the same drop height. This would mean I could calculate the efficiency of the balls I used. What’s more I could change how I measure the height it bounces back, or actually what I measure. I could measure the efficiency of the ball, and how the height I drop it from affects the amount of energy is lost.