4. Discussion

Key findings & Analysis of results


We found out that there is a steady increase of the rebound height of the fishball from 0.667 cm for 0 grams of gelatine to 7 cm for 5 grams of gelatin. However, there is a significant increase of the rebound height to 11 cm for both 6 and 7 grams of gelatin. For 8 and 9 grams of gelatin there is a significant drop to 3.33 cm for the rebound height compared to the trend.


Explanation of key findings


From 0 to 5 grams of gelatin, the rebound height increased steadily from 0.667 cm to 3.333 cm. This is due to the increase in the binding strength of gelatin when more of it is added. Hence, when the fish balls make impact with the wooden surface, some kinetic energy can still be converted back into gravitational potential energy when rebounding.


From 6 to 7 grams of gelatin the rebound height significantly increased to 11 cm. This is the maximum point at which most of the kinetic energy of the fish ball can still convert to gravitational potential energy. The force required to breaking the binding of gelatin is still larger than the weight of the fish ball.


From 8 to 9 grams of gelatin, there is a significant drop of rebound height to 3.333 cm. By this point, the weight of the fish ball is a strong enough force to break the binding of gelatin. Hence, the fish ball decreases in rebound height.


Evaluation of Hypothesis


Once again, this is our hypothesis: the more gelatin added to the fish paste, the higher the rebound height of the fishball will be until a certain point where the more gelatin added to the fish paste, the fishball will decrease in rebound height. We believe so because there will certainly be a point at which the total weight of the fish ball is a stronger force than the force required to break the binding of gelatin. Hence, that limit prevents the fish ball from continuously increasing in rebound height while the gelatin content of the fish ball increases. Therefore, there will also be a point where the rebound height is zero because the fishball covered in gelatin splatters upon impact with the wooden surface.


Our results supported the hypothesis very well but there were two experimental errors which will be elaborated in the next section.


Limitations and Areas for improvement


The first limitation we had was that we could not get transglutaminase powder in time for the submission of this project, also raw meat was not allowed because of hygiene reasons. Thus, gelatin and fish paste replaced them respectively.


The different fish balls are of different shapes and they are not a perfect sphere, hence when the fish ball bounces on the wood, most of them bounced off and was stopped by the two wooden planks of the walls of the wooden structure, this in turn will affect the rebound height of the fishball and make the experiment unfair. Therefore an area of improvement is to use a fixed sphere mould instead of cling wrap to house the fish ball when it is inside the fridge. This will make sure that the fish ball are all of a definite sphere and errors like this would be reduced significantly. Another area of improvement is the placing of the fishball above the wooden surface. This may have caused the fishball to hit the wooden walls that prevent the fishball from bouncing out or not and that makes the experiment unfair as the fish ball loses some gravitational potential energy to sound and heat energy due to friction with the walls. This could also be the reason why the rebound height of the 6 and 7 grammes of gelatine fish ball and the 8 and 9 grammes of gelatine fish ball had a sudden decrease.

We also felt that the ratio between fish meat and gelatine can be a better gauge to be investigated next time.

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