Apparatus
- Ramp that has been graved in a straight line to provide a course for the ball to roll through. (length of ramp is 200cm)
- Squash Ball (24.43 grams)
- Stop Watch (2.d.p accuracy)
- Building Blocks that are 8.2 cm in height each.
Prediction
I predict that the increase in the ramps angle is proportional to the speed of the ball. So if the angle increases the speed of the ball increases too. If the ramp was completely horizontal (angle 0o) the velocity of the ball would be zero as there would be no way of the gravitation pulling it through downwards, but if the ramp was put to a small gradient the ball would roll down slowly, and as you increase the gradient the speed of the ball increases too. But when the ramp is put vertically (900) the ball would free fall at the speed of gravity (9.81 m/s), due to the ramp not being there to put friction against the ball, and to deflect its course to another direction. As I would get different speeds, as I differentiate the steepness of the ramp, I will have to work out the mean speed using an equation which is the following;
Mean speed (m/s) = Distance Traveled (m) X Mean Time Taken (S)
Secondly I predict that as the Gravitational potential energy increases, the kinetic energy also increases proportionally
Thirdly I predict that as the height of the ramp increases the G.P.E also increases proportionally
Fourthly I predict that as the speed of the ball (squared) increases the kinetic energy exerted is also increased proportionally.
Fifthly I predict that as the kinetic energy increases the friction force also increases, and that the friction force is greater than the kinetic energy.
So to work out the G.P.E I would use this formula;
G.P.E (j) = Weight (N) X Change in Height (m)
But to work out the weight I would first have to use this formula;
Weight= Mass (kg) X Gravity (N/Kg) Where the gravity is constant at 9.81N/Kg
To work out Kinetic energy I would use this formula;
Ek (j) = ½ Mass (Kg) X Speed2 (m/s2)
And finally to work out the Friction force I would use;
Friction Force (j) = G.P.E (j) – K.E. (j)
Number & Range of Readings
As my main non constant value would be the height, I will have to choose the heights that I'm able to have using the building blocks. I will have six different heights which I think would give me a large range of results. The heights would be 8.2, 16.4, 24.6, 32.8, 41 and 49.2 centimeters. To work out how big the angles are I have to use this formula;
Angle = sin-1(Opp/Hyp)
Angle = sin-1(height of ramp/200)
So the angles of the heights are;
For each height I think a suitable number of readings would be five of each height, which would make any anomalous results appear clearly, and would also when taken out average would get rid or minor errors
Methodology
Firstly I would collect the apparatus, and then I would set it up. (As shown below.) then I would with a red marker, mark down the starting point, then the end point which is exactly 200cm. I did this so that I’d be able to start the ball from the same position, and end it the same for all the tests. After it being set up, I draw an empty table of results, so that I would fill it in as I do each experiment. Then I would place the squash ball which is 24.43g and has a diameter of 3.9cm. at the starting point, and hold it with one hand, and have my other hand on the stop watch so that I let go of the ball, and start the stop watch together, to get rid of ad much human error, then I would stop the stopwatch as the ball crosses the finish line, which would be placed 200cm after the starting line. I would repeat that for every height respectively, five times each. After I finish all the heights, and all their repeats, I would take apart the apparatus carefully, and place each part in its designated place.
Safety
One of the most important aspects of the experiment is safety. As it would be the safety of my colleagues in the class. So I would have to handle every thing very cautiously incase the ramp or the building blocks fall on someone and injure them. So I will have to do my best to avoid such accidents from happening.
Obtaining Your Evidence
Results;
Weight = 0.2343 X 9.81
Weight = 2.298483 Newton’s
G.P.E Results; G.P.E (j) = Weight (N) X Change in Height (m)
K.E Results; Ek (j) = ½ Mass (Kg) X Speed2 (m/s2)
Friction Force Results; Friction Force (j) = G.P.E (j) – K.E. (j)
Analyzing your Evidence & Drawing Conclusions
Graph number one, provides evidence for my first prediction, which is that as the angle of elevation increase the speed of the ball increases too. And the graph shows that by starting first starting off, and going in a positively skewed straight line. This happened because as the angle increases the G.P.E increases and the friction force acting on the ball decreases because the gravity force strengthens.
Graph number two, shows that as the G.P.E increase the Kinetic energy increases. Because if we increase the height of the ramp, the G.P.E would increase proportionally as we would see in graph three. And when the G.P.E increases this means that when the object is moving downwards the kinetic energy also increases, because there would be more speed when rolling down. And that graph and results fully support my prediction number two, which states that when Gravitational potential energy increases the Kinetic energy also increases proportionally.
Graph number three, shows how the G.P.E is affected by the height of the ramp in centimeters. And the graph shows a positive gradient of 0.23J/cm this means that every centimeter you increase on the ramp that I'm using the gravitational potential energy increases too by 0.23 joules. And that supports my prediction number three, which was as the ramp height increases the G.P.E increases also proportionally. Which also shows that the further away the object from the ground the more G.P.E it’s got stored in it, ready to be let out as Kinetic energy.
Graph number four, after working out the gradient on the graph, shows that as every one joule is added, would increase the speed of the ball by 9m/s. which supports my prediction number four which states that as the speed of the ball increase would mean that the kinetic energy would also increase proportionally. And that also proves that if an object wanted to move it would need a specific amount of kinetic energy but if it wanted to go faster or stronger, it would need more kinetic energy, that statement works both ways.
Graph number five, shows the proportionality between the friction force and the kinetic energy. And the graph shows that at small amount they are proportional but when they increase the friction becomes bigger than the kinetic energy, in which that decreases the efficiency, and loses energy as heats energy.
K.E *100 = percentage useful energy used
G.P.E
0.024051*100=24.051/0.188476=12.76% percent of the G.P.E transforms into useful kinetic energy, the rest 87.24% is wasted as heat energy. And that proves my last prediction which states that the friction force is greater than the kinetic force!
Evaluating Your Evidence
During this experiment I have tested the relationships between the height of a ramp and the speed of a ball rolling down it. Through this I have come in to contact with the G.P.E, K.E. and the Friction Forces. Which occurs relying on the variation in the height of the ramp and the speed of the ball. All my predictions have been proved using the graphs and the results, as my results were very accurate except for a couple of anomalous results occurring. These anomalous results may occur due to…:
- Timing the stop watch incorrectly, for example, letting the ball roll first then pressing the start button on the stop watch a quarter of a second later may alter the tests accuracy dramatically.
- The grooves on the ramp might have parts that decrease the speed of the ball.
- The ball was not accelerating the whole time at the same acceleration, which that would make a difference when it came to do the calculations.
I don’t think repeating any more test for results would make it more accurate cause I’ve already had carried out 5 samples of each test.
I think I have carried out a suitable range of results but there was an area for improvement as I could have investigated larger heights, which would mean larger angles.
Improvements
Things that I would improve in this experiment are;
- Lager range of heights and angles
- Larger variety of ball to use
- A different surface for the ball to roll on, a smoother surface, such as plastic, or metal, with would reduce friction
- A stop watch that is connected to the computer, and uses lasers to start and stop the stopwatch when the ball rolls through them.
- Shorter ramp to keep the ball accelerating.
The whole experiment was a success in that I gained knowledge of things I didn’t know before, I have carried out the experiment safely, fairly and accurately.