PhysicsQuest: Gravity and Orbits

Using the links provided, answer the questions below regarding gravity and orbits.  If the links aren’t working, find another page with the necessary information.

  1. What are Kepler’s 3 Laws of orbital motion? Include an equation in your definition of the 3rd  Which conservation law is the reason for his 2nd law? 
  2. Describe the experiment Henry Cavendish used to find the value of the universal gravitational constant G. Include a diagram and explain how the apparatus worked. 
  3. You Do It: Once Cavendish determined the constant G, physicists were able to find the mass of the Earth for the first time. Assuming you know the radius of the Earth, derive an equation that will let you find the mass of the Earth. (hint: the force of gravity has multiple equations, but they all mean the same thing)
  4. Scientists don’t know how gravity is transmitted (how does one mass “feel” the other), but they think it may be through gravitational waves. What are gravitational waves?  Describe 5 possible sources of gravitational waves?

  5. One facility trying to detect gravitational waves is named LIGO. Describe the LIGO experiment and how it hopes to detect gravitational waves. 
  6. Show your work: Calculate the force of gravity between the earth and the sun. (look up any values you need)
  7. Show your work: Calculate the force of gravity between the sun and the star Sirius.
  8. Show your work: Using Kepler’s 3rd law, the semi-major axis of the Earth’s orbit, the period of the Earth’s orbit, and the semi-major axis of Jupiter’s orbit, calculate the period of Jupiter’s orbit.

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