# Investigate a factor that might affect the size of a crater made by a falling object.

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Introduction

Aim Investigate a factor that might affect the size of a crater made by a falling object. Prediction and Hypothesis This investigation is to help prove the fact that the higher the height from which an object is dropped from affects the size of the crater it makes up until a certain height when the object has enough falling distance to reach it's terminal velocity. All objects have gravitational potential energy, given by the weight x height (PE = WH.) Therefore, potential energy is proportional to the weight and proportional to the height (PE W, PE H) so, an increase in weight or height results in an increase in potential energy. As the object falls it loses PE because the height is decreased yet gains kinetic energy, one, because it is accelerating and two, due to the law of conservation - that energy can't be created or destroyed, just transferred. The kinetic energy is added up as the object gets faster yet the rate of acceleration gets slower because less and less energy goes to kinetic with more being given off as heat and sound due to an increase in speed and friction as the object falls, consequently, the object is sill getting faster but not as quickly. The same theory can also be used with forces; every object has a downward force called weight, which is caused by gravity acting on it. An opposing force called air resistance, which acts against the direction an object is moving, also affects it when falling through the air. As an object falls it accelerates downwards but as the speed increases so does the air resistance because there is more friction between the object and the air. This means that the object does continue to get faster but the rate of acceleration decreases due to an increase in air resistance. When both the upwards and downwards forces acting on the object are balanced, the object stops accelerating and the rate of acceleration becomes 0m/s2, it now falls at a steady speed - it has reached it's terminal velocity (a maximum velocity.) ...read more.

Middle

lowest and highest heights) and has an interval increase of about 5mm. Whereas, graph B shows a strong line of best fit though the middle results (e.g. 1-2m) with an interval increase between the results always around 10mm. The results at the higher heights on graph A would be less on graph B and the results at the higher heights on graph B would be less on graph A. It seems that a graph in between these two graphs would be a more accurate reading of the results and the intervals of increase would be the same each time, the two graphs drawn are another way to show the error in the results such as the percentage error due to the fact that more than one line of best fit could be followed showing different anomalies. Out of the two graphs however, graph A is probably the most accurate with the results that lie on that line only having a percentage error of about 5-6%, whereas, the results that lie on line B have percentage errors ranging from 6-15% again, this is the middle results which have the largest interval increase between them. The results follow the prediction and predicted graph almost exactly up until a certain point. An increase in the height resulted in an increase in the depth of the craters this is because all objects have potential energy, which is proportional to our dependent variable the height because the PE=W x H, therefore potential energy is also proportional to the weight, yet this variable was not investigated. As the object falls, obviously the height is decreased resulting in a loss of potential energy which becomes kinetic energy due to the law that energy can never be crated or destroyed and also the fact that the object is moving and accelerating. Overall, the higher the object is dropped from the more PE and then KE it has so the more it accelerates and faster it moves, the more energy it has on impact and the larger the crater - this was what the experiment helped to prove. ...read more.

Conclusion

Increasing the surface area of the object will also help to increase the air resistance having the same effect as dropping the object with a parachute, however, a flat shape would make it harder to measure the depth of the crater especially if it is thin so if that option is chosen then it may be a better choice to measure the diameter of the crater instead. Although a pre - test would still need to be carried out to determine the best variable to measure and the equipment and method to be used. The other final option that could be done is dropping the object through water, which is much denser than air, the object will displace the water creating up thrust and because water is so dense the up thrust will be greater than air resistance in air. Both forces will increase at the same rate until they are even when the object will continue to move at a steady speed and stop accelerating, because the up thrust is greater than air resistance this should happen sooner and from a lower height, therefore it will be possible to see if the object reaches its terminal velocity and then to try and make an estimate of the height at which the object will reach its' terminal velocity in air by calculating how many times denser water is than air and then multiplying that answer by the answer for the terminal velocity. There are however, many possible problems with this experiment, for example, it would be difficult to measure a crater depth or diameter yet, a possible way around this might be to measure the speed of the object with a small speed sensor just before impact at various heights with an aim to see if the object finally stops accelerating and always hits the bottom at the same speed, thus meaning it has reached its' terminal velocity. Charlotte Swain Physics Homework ...read more.

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