# Physics Investigation: Speed

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Introduction

Physics Investigation: Speed

In this investigation I am finding out how the height of a ramp affects the speed of a toy car.

To do this, I first need to know about speed and gravity.

I know the equation for speed is: Speed = Distance

Time

From that equation I can now work out what the speed of the toy car will be, when I know the distance the ramp is and the time it took the car to come down the ramp.

Now, gravity is a bit more complicated: Over three centuries ago, Isaac Newton invented a new kind of mathematics called calculus so that he could model motion in the natural world using mathematics. Calculus is about measuring change and so calculus became a vital tool in describing the motions of simple objects.

Newton was able to make a mathematical model that encompassed both objects falling because of gravity on Earth, and the motion of heavenly bodies in the skies. Newton decided that the force of gravity on Earth was the same force that organized the motions of the moon around the Earth and the Earth and all the planets around the sun. He invented a formalism and developed mathematical formulas for calculating the size of the gravitational force both on Earth and in outer space.

This (more simply) means that there is a force in the Earth that attracts all objects to it, so that they (or we)

Middle

1.41

1.56

67.34=67

50

100

0.74

0.49

162.60=163

78

100

0.45

0.38

240.96=241

From this preliminary test I found out that I should go from 5 to 70cm in height, because if it was higher it would be too hard to measure as it is too fast and it won’t be precise. If it was too low, the car might not start running and you might have to push it so it wouldn’t be a fair test.

Obtaining Evidence: Results

Height (cm) | Distance (cm) | Time 1st (secs) | Time 2nd (secs) | Average Speed ( s= d ) t (cm/s) |

5 | 100 | 2.46 | 2.32 | 41.84= 42 |

10 | 100 | 1.40 | 1.27 | 74.91=75 |

15 | 100 | 1.26 | 1.01 | 88.11=88 |

20 | 100 | 0.98 | 1.04 | 99.01=99 |

25 | 100 | 0.80 | 1.09 | 105.82=106 |

30 | 100 | 0.66 | 0.52 | 169.49=169 |

35 | 100 | 0.68 | 0.66 | 149.25=149 |

40 | 100 | 0.78 | 0.80 | 126.58=127 |

45 | 100 | 0.54 | 0.59 | 176.99=177 |

50 | 100 | 0.51 | 0.53 | 192.31=192 |

Anomalous results repeated

Height (cm) | Distance (cm) | Time 1st (secs) | Time 2nd |

Conclusion

I think we should have repeated the experiment more than twice, because as you can see in the graphs, only by repeating the anomalous results another two times, it made them fit into the relationship, when they didn’t before.

From this I think that it isn’t very reliable, as the anomalies changed very easily, the same way in which they could have changed to not fitting into a pattern again. But, the experiment is reliable enough to support the conclusion that the higher the height the faster the speed, because it worked like that most of the time. My conclusion is reliable enough to show to other people and trust it is right and that that is the way it will always work.

Further work that could be done to provide additional relevant evidence could be to do the same thing with a longer ramp and increase the height up to the point when the ramp was a straight line, so that would be the maximum speed. You could also change the surface of the ramp to see which surface made it go faster, or do it in different places, where it is windy, or sunny, or cold, hot the wind blowing east, west south or north. The (toy) car could have different weights and you could look at which one went faster, the heavier one or the lighter one.

By Maria Guisasola, 9.1.

This student written piece of work is one of many that can be found in our AS and A Level Mechanics & Radioactivity section.

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