3 How would you work out the amount of weights the students should put on the rubber sheet to represent the mass of the other celestial bodies?
They continue with their task as follows: zz
zz zz They place a marble at the point A while the sheet is flat and pulled tightly.
They record the time it takes for the marble to move to position B when the weight is added to the centre of the sheet.
The test is repeated for each celestial body listed in the table. 4 What does the movement of the marble represent in this model?
5 Predict in order of the fastest to slowest the time it will take for the marble to move from A to B for the different runs of this test. Explain the reasons for your prediction.
Marble A B Weight z Fig. 21.5.2
What makes a planet a planet?
Remember that a defining feature of a planet is that it can clear the space debris in its orbit. This means that it has become gravitationally dominant.
6 Does this model help to explain why the Earth and Venus are classified as planets but the Moon and Pluto are not? Why?
7 Remember that a model should help to explain natural phenomena in a simpler way. Is this a good model for representing the nature of the gravitational field around celestial bodies of different masses? In what way? What improvements could you make to this model to represent the nature of the gravitational field?
Set up this model in class. Collect relevant data for the time it takes for the marble to move from A to B and present the data in a clear way. Record your trials and use video evidence to back up your reported findings.
