Physicals Essay

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Physics coursework

The Experiment

Our experiment is to investigate the time it takes for an object to free fall and from our results work out a value for gravity. The experiment will include us dropping a golf ball from a different height and measuring the time it takes to pass through a light gate.

Our hypothesis for the experiment is that as the drop height of the golf ball is increased the velocity of the ball will increase, this is because it has more time to accelerate. We hope to find out from our results that the golf balls acceleration is the same as gravity which is 9.81 ms². We intent on showing this through the Suvat equation which is V²=U²+2as where ‘a’ is acceleration. Suvat equations were made by Gottfried Leibniz, Suvat stands for displacement (S), Initial velocity (U), Final velocity (V), Acceleration (A) and Time (T). As I said we are using the equation V²=U²+2as, but we have to re-arrange this equation to find ‘a’, this re-arranges to be a=(V²-U²)/(2s).

We are doing two experiments, the first one we are doing includes dropping a golf ball from a variety of different heights and only measuring the results with one light gate, in this experiment ‘U’ the initial velocity is always zero which means the Suvat equation is a=V²/2s.

In the second experiment we are using two light gates instead of one, similar to the first experiment we will be dropping a golf ball from various different heights and recording the times at each light gates, the difference between this experiment and the first experiment is that ‘U’ the initial velocity is the value at the first light gate, so the Suvat equation returns to the original a=(V²-U²)/(2s).

In this experiment the dependent variable will be velocity of the golf ball as it travels through the light gate and as the drop height changes, this is the variable that will be measured. The independent variable will be the height the ball is dropped from as this is the variable that will be changed. There are also quite a few controlled variables these are components of the experiment that are kept the same throughout, these variables are:

* The diameter of the ball – If the diameter of the ball changes it will affect the value for gravity, firstly because the time the ball will take to get through the light gate will change proportionally and secondly then finding the velocity you have to do divide the diameter of the ball by the average time, so this result will change accordingly. * Make sure the ball is dropped straight – If the ball isn’t dropped correctly it could lead to the ball bouncing off the insides of the tube, which will slow the ball down making the experiment unreliable. * Having the same person dropping the ball – If you have a different person dropping the ball they could have a different perception of what the drop height is. * Make sure the ball is dropped from the same height – This point also links in with the previous point, if the ball isn’t dropped from the same height the ball could have more/less time to acceleration to its maximum velocity, this is why the ball should be marked with a black line around the diameter to make sure it is dropped from the same height. * The tube is straight – The tube must be perfectly vertical, if it isn’t the ball could bounce or roll down the sides of the tube and if this happens it could cause unwanted friction on the ball causing it to dramatically reduce its velocity and taking the ball much longer to accelerate to its maximum velocity. * Keeping the light gates horizontal – If the light gates aren’t kept perfectly horizontal the gate might not be a to read the whole diameter of the ball as it passes through, this can give the perception that the ball is travelling much faster than it actually is making the results invalid. * The ball’s initial velocity – The initial velocity of the ball must be zero, this is achieved in the experiment by dropping the ball. But if the ball is...
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