Preliminary Work
I experimented with three types of ball and three types of surfaces. A rubber ball, a golf ball and tennis ball on wooden, concrete and carpeted floors. I looked at several different aspects, how lively the ball was on that surface, the variation in bounce heights and ease of measurement. I dropped the ball from 1, 1.5 and 2 meters. The results were as follows.
Rubber Ball:
Golf Ball:
Tennis Ball:
I concluded from this that the best surface to use was that of concrete. This also shows us that the concrete floor is harder than the wooden and carpet floors. I also found that both the golf ball and rubber ball gave a good variation in bounce heights and could be measured easily. I will choose the rubber ball over the golf ball due to safety reasons as the golf ball is very hard and could potentially cause damage.
Plan
I will start by placing a rubber ball in a clamp attached to a stand. I will then adjust the height of the stand to the desired height measuring from the bottom of the ball to the floor. The clamp will need to be situated next to a wall so that the height of the rebound can be marked on the wall and then measured with a meter stick. When the ball is at the correct height, the clamp is loosened until the ball falls. The above information needs to be recorded. I will repeat the experiment at heights of 1, 1.2, 1.4, 1.6, 1.8 and 2 m. I will repeat the entire experiment four times so that I can get a more accurate set of results.
Equipment:
- A bouncy rubber ball
- 2 meter rules
- A clamp and stand
- A marker pen
Results
Conclusion
From my graph I have found that if I increase the height the ball was dropped from then the height of the bounce will also increase. Therefore the input variable is proportional to the outcome variable. The straight line of the graph remains constant throughout. As I stated in my prediction, the ball will bounced to a height less than its original height due to gravitational potential energy being converted into thermal energy.
The ball gained gravitational potential energy when it is lifted off of the floor, some off this energy was converted into heat energy due to friction and compression/expansion. The higher the ball is dropped from the more gravitational potential energy will be gained, this means that the velocity of the ball will be greater the higher it is dropped from. As Hooke’s Law states: “Within an elastic limit, the extension of a material is proportional to the applied force.” This can be related to our ball bouncing. The greater the velocity the greater the force exerted on the ground which causes a greater compression and expansion of the ball propelling it to a higher bounce. This evidence almost entirely backs up my original prediction, however I found that the height the ball is dropped from is not directly proportional to the height of the bounce.
Evaluation
The evidence I have found is quite reliable as the error bars on the graph are close together. The experiment was fairly hard to conduct as accurately as possible as the measurement of the ball bouncing had to be estimated to the nearest centimetre as we only had our eyes to see where the ball bounced to. This meant we had to make the decision in a split second. This therefore may have caused our results to be slightly inaccurate. Occasionally the ball would scrape against the wall causing extra friction which would affect the results, so therefore I repeated the drop so that it was fair. The ideal way to measure these results would be to film each drop and play back the bounce in slow motion and pause it at the frame where the ball reaches its highest point. Due to time allocations and school facilities this would not be possible. The ball should be as round as possible so that any small bumps do not affect the bounce. The only possible anomaly was the 77 and 89 cm bounces for the 1.4 m drop. These caused the error bars to be slightly bigger than on the other results. This may be down to the difficulty of observing the bounce height or a slight change in drop height.