# Investigate and measure the speed of a ball rolling down a ramp.

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Introduction

Khalid Abu Rumman GCSE Physics Coursework Mr.Evison

11s

Introduction

In this piece of coursework I’m going to investigate and measure the speed of the ball rolling down a ramp. From the data that I’m going to collect I’m going to be able to work out the Gravitational potential energy when changing the height, the friction force acting on the ball whilst it rolling down, and finally the kinetic energy exerted by the ball.

Planning

Fair Testing

Before I would start the experiment I would have to devise a suitable method that would provide a safe test, which is fair and accurate. In this experiment I’m going to have to roll down a ball whilst changing the angle of elevation of the ramp, and the factors that would have an effect on the accuracy of the output results are;

- Size of the ball
- Heaviness of the ball
- Length of the ramp
- Height of the ramp
- Texture of the ball
- Smoothness of the ramp
- Angle of ramp from the ground surface

Here in this experiment the only factor that I'm going to change would be the height of the ramp which in turn would affect the angle of the ramp too, if the length of the ramp stays constant.

For the experiment to be a fair one I have to;

- Keep all the factors that affect the experiment constant except the ones that I'm testing.
- All the experiments have to be done by the same person on the same day, because if we changed the person that is doing the experiment it may lead to different reaction times making the experiment inaccurate
- All I have to change is the height of the of the ramp from the ground it’s resting on. And by keeping the length of the ramp constant that would in turn proportionally change the angle of the ramp.

Middle

5.16

2.75

2.89

2.75

2.79

Above are the preliminary results.

Selecting the most Suitable Apparatus

When looking at the preliminary results the golf ball traveled too fast for us to be able to stop the time accurately, the table tennis ball was too light so has gone off course most of the time, due to the air resistance, and that was enough to deflect it. The tennis ball was too big and I don’t think it would be a good idea to use it, as we would find it hard to place correctly on the starting point line, and it would take too much time which might lead to anomalies. But the squash ball to me was the most suitable ball to use, and it stays in its path all time which is in a straight line down the ramp. In the preliminary tests we used 3 cm think books to lift up the ramp, but I don’t think that that would be a good idea, because the books might be compressed a bit, which would decrease the height we are aiming to achieve. So I think I'm going to use building blocks that are 8.2cm in height each and that would cancel out the chance of any change in the height due to compression. When thinking about time, the most accurate stopwatch we can get would be a 2 d.p. stopwatch and that’s all we’ve got. There are lots of different types of ramps out there, with different types of surfaces but the only one that was available to me was a wooden ramp that has a groove going through it, to provide a path for the ball to roll through. Below is the apparatus that I'm going to use to do the experiment.

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.

Number | Predication |

1 | As the angle of the ramp increases the speed of the ball increases proportionally. |

2 | As the Gravitational potential energy increases, the kinetic energy also increases proportionally |

3 | As the height of the ramp increases the G.P.E also increases proportionally |

4 | As the speed of the ball (squared) increases the kinetic energy exerted is also increased proportionally. |

5 | 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;

Height (cm) | 8.2cm | 16.4cm | 24.6cm | 32.8cm | 41cm | 49.2cm |

Angle (Ø0) | 2.3490 | 4.7030 | 7.0650 | 9.4390 | 11.8290 | 14.2410 |

Conclusion

- 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.

Khalid Abu Rumman - -

This student written piece of work is one of many that can be found in our GCSE Forces and Motion section.

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