Mass – the heavier the ball is the faster it will fall due to the gravitational pull of the earth
meaning it has weight as well.
Prediction.
I predict that the higher the ball is dropped from the higher it will bounce because the ball will gain more kinetic energy on the way down because potential energy equals to mass multiplied by gravity multiplied by height (PE=mgh) and height is the easiest factor to change out of the three.
Method.
I will set up the apparatus as shown below. Then I will drop the ball from 5 different heights, 5 times each. The ball will be dropped from between two rulers that will part so that the ball will have the least amount of spin possible and won’t have any force put onto it, making it a fair test. The ball will bounce once and then the height of that bounce will be recorded against a ruler by having my partner looking at the area of which we have figured out by bouncing the ball once for a practise. This has been done so that there are no parallax errors.
Diagram.
Apparatus.
- Retort stand
- Clamp
- Boss
- Ruler – 1m
- 2 rulers – 15cm – balance the balls on
Preliminary experiment.
Before doing the actual experiment we did a practise experiment using a computer simulation that dropped the ball for us then stopped it once it was at the top height of its bounce, and then we could zoom in to see the actual height. These are the results:
Seeing that these results were collected by measuring the bounce on a computer the results are not reliable because of the random selection of heights made by the computer. Also the simulation doesn’t take the force of gravity or air resistance into consideration and this makes it even more unfair. Fortunately, my results were close together so I could use them all in my average, but if any results were too far out I wouldn’t have used them to figure out the average.
Results.
These were the actual results collected by me and my partner:
Conclusion.
From looking at my results table and graph I can clearly see that the higher the ball is dropped from, the higher it will bounce. This concludes with my prediction that in the equation PE=mgh and in general, the height the ball is dropped from is a very effective variable that can change the height the ball bounces. Also, from looking at my graph I can see that my results aren’t very scattered, therefore are reliable.
Evaluation.
Having drawn up my conclusion, I can now write about the quality of my investigation fully.
Shown by my results table and graph, the results that I collected were fairly accurate but due to how we took the results down (by looking at the ball next to the ruler) it is clear that it would be better if we used something like a video camera and took the results down by looking at that in slow motion. This would have been more accurate because it would have gotten rid of the parallax error easier and it would be easier to read due to the lack of focus the eye has when looking at something close and something farther away, at the same time, and this would stop that from happening. The ball is also going up and back down again so fast that it is virtually impossible to tell the exact height with the naked eye.
The only seemingly odd result was the last result taken on the height 100cm because it was 0.6cm away from the nearest result which was the furthest away from any other in all of the results that we recorded.
I believe that we repeated the test enough times to get reliable results but if we had the time I would do it another 10 times to just increase that reliability just a bit more. I believe we could have improved the method in several areas. The first I have already mentioned, which is video taping the bounce so that we can get clearer results to get a more reliable average. The other way would could have improved on the experiment was when we dropped the ball – it could have been more accurate where we dropped it and how we dropped it. You see, we could have made a holder for the ball that had a trap door at the bottom and was held by a boss and clamp, to make the height more reliable, and then when the ball was released the timer would start.
My graph shows that the results had a certain pattern being that they steadily increase as the height of the drop is enlarged and towards the end start to round off. The curve is most probably due to an increase in air resistance because of the increased drop height and would eventually level off more because of this. If I could of I would have done more heights, most probably up to 200cm, just so I could see if the results do level off more as the height is increased.
If given time I would have liked to investigate more of the variables, especially mass and temperature. These would have been difficult to do but would give more reliability to my results.
