# The purpose of this experiment is to observe the acceleration of an object caused by the Earth's gravity.

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Introduction

Aim: The purpose of this experiment is to observe the acceleration of an object caused by the Earth's gravity.

Introduction:

Gravitational acceleration, the acceleration caused by the gravitational attraction of massive bodies in general.

Gravity of Earth, the acceleration caused by the gravitational attraction of the Earth.

Standard gravity, or g, the standard value of gravitational acceleration at sea level on Earth (9.80665 m/s2)

Hypothesis:

The acceleration of gravity is 9.8 m/s2 near the Earth's surface and when air resistance is negligible.

Materials:

- small, dense weight (200 g) - a dense weight will experience the least air resistance for its mass
- electric buzzer - vibrates at the same rate as the alternating current (AC) which is 60 Hz
- ticker tape
- carbon paper disk
- retort stand
- duct tape
- school bag (for soft landing)
- ruler

Method:

- Use duct tape to attach the buzzer to the retort stand so that the part where the ticker tape goes through is sticking out over the edge of the lab bench.

Middle

33.8 cm

77.2 cm

338 cm/s

0.4 s

0.5 s

0.45 s

0.1 s

41.7 cm

118.9 cm

417 cm/s

Analysis:

Acceleration = (change in speed)/(change in time)

From our observations, we can calculate four or five (assuming initial speed of 0 cm/s) values of acceleration. For example:

Acceleration = (145 cm/s - 51 cm/s)/(0.15 s - 0.05 s) = 940 cm/s2

The first interval is smaller than the others:

Acceleration = (51 cm/s - 0 cm/s)/(0.05 s - 0.00 s) = 1020 cm/s2

The following table shows the acceleration calculated for each interval:

Interval | Acceleration |

0.0 s | 1020 cm/s2 |

0.05 s | 940 cm/s2 |

0.15 s | 930 cm/s2 |

0.25 s | 1000 cm/s2 |

0.35 s | 790 cm/s2 |

Average | 936 cm/s2 |

The following graphs show the position of the weight and the speed of the weight during the 0.5 s that the weight was falling. The acceleration of the weight is represented by the slope of the speed-time graph.

Position-Time Graph:

Speed-Time Graph:

The speed-time graph shows that the line of best fit through most of the points has a slope of approximately

(430 cm/s)/(0.45 s) = 956 cm/s2

Conclusion

It is usually better to take a lot of measurements than just a few. In this lab, you could have exchanged results with other members of your team (since each member of the team should have had their own ticker tape to measure). In this way you could have had 15 or 20 acceleration values instead of just 5. For example:

Person 1 | Person 2 | Person 3 | |

Interval | Acceleration | Acceleration | Acceleration |

0.0 s | 1020 cm/s2 | 1020 cm/s2 | 760 cm/s2 |

0.05 s | 940 cm/s2 | 940 cm/s2 | 850 cm/s2 |

0.15 s | 930 cm/s2 | 900 cm/s2 | 890 cm/s2 |

0.25 s | 1000 cm/s2 | 1030 cm/s2 | 930 cm/s2 |

0.35 s | 790 cm/s2 | 790 cm/s2 | 830 cm/s2 |

Average | 936 cm/s2 | 936 cm/s2 | 852 cm/s2 |

From this table we can calculate an overall average acceleration of 908 cm/s2. this is actually LESS accurate than the first set of results, because the third member of the team had the poorest accuracy. However, it does indicate a systematic error: all the results are giving an acceleration less than our hypothesis. To reduce this error, we should look for factors in our experiment that were slowing the weight - for example, friction.

This student written piece of work is one of many that can be found in our International Baccalaureate Physics section.

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