Gravity Simulation

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Gravity Simulation
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Gravity

• Gravity is the weakest of the four fundamental
  forces.
• Gravity is responsible for the attraction of
  massive bodies.
• Gravitational force is always attractive and acts
  along the line joining the centres of mass.
• Gravitational force is responsible for the
  formation of planets, stars and galaxies.
• Gravity decides the orbital paths of the planets
  and moons in our solar system.

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Newtons Law of Universal Gravitation

• The gravitational force between the two masses
  m1 and m2 is described by Newtons Law of
  Universal Gravitation.
• G is the universal gravitation constant.
• This relationship is an example of an inverse
  square law force.
• Forces are equal in size but in opposite
  directions.

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Setting up the Experiment

• This learning scenario requires flash player 10.
  
• Go to http//get.adobe.com/flashplayer/ to
  download and install this software.
• Extract the gravitysim.zip.
• Run gravitysim.swf.
• To carry out the experiment you will also need a
  stopwatch.

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The Experiment

• Drop the ball from a set distance and measure the
  time it takes to hit the bottom of the box.
• Repeat your measurements several times and record
  them on the worksheet.
• Repeat for each of the nine environments which
  have gravity.
• Experiment with how the ball reacts in each of
  the environments by throwing the ball with the
  mouse and note how this differs from Earth.
• Analyse the results to obtain the value of the
  acceleration due to gravity for each planet.

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Analysing the Results

• Values for the release height and the time taken
  to fall can be used to calculate the acceleration
  due to gravity for each of the planets.
• If it assumed that there is no air resistance and
  no other downward force, the acceleration due to
  gravity g is equal to a.
• Since the ball has no initial velocity, u 0,
  the displacement, S, can be treated as the drop
  height, h.
• (Eq.1) can then be rearranged to allow
  calculation of the acceleration due to gravity
  (Eq.2).

Eq.1
S Displacement u Initial velocity a
Acceleration t Time
Where
Eq.2
h Drop height g acceleration due to
gravity t Time
Where
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Discussion after Experiment

• In terms of gravity, which of the environments
  are most like Earth and which are the most
  different?
• Why does gravity vary on other planets?
• Was the gravity more difficult to measure on some
  planets more than others?
• What are the sources of error?
• Was there more variation in your results in
  certain environments?

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Questions, Exercises and Tasks

• Use the internet to find the difference in the
  diameter of Uranus and Earth? Given the large
  difference in diameter, why is the gravity
  relatively similar?
• If a man weighs 80Kg on Earth, how much will he
  weigh on the other planets in the Solar System?
• Look up the other equations of motion, what other
  systems could they be applied to?
• Investigate some of the ways that the value of
  the gravitational constant, G, can be
  experimentally determined.

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