0. Many roller coasters use magnetic brakes to slow the train at the end of its run. A conducting plate on the train passes by powerful magnets fixed on the track. a. Explain the principle behind this magnetic braking. b. The system needs an ordinary friction-based brake to bring the train to a full stop. Explain why the magnetic brake is not very efficient when the train is moving slowly

Can you answer problem 4? Can you also provide a short explanation for the answer you chose?

According to Lunar Laser Ranging experiments the average distance L M from the Earth to the Moon is approximately 3.85 x 105 km. The Moon orbits the Earth and completes one revolution in approximately 27.5 days (a sidereal month). How can the mass of the Earth be calculated using the information above? Select the correct statements. Select one or more: a. Use Newton's third law. b. Use Coulombs law. c. Use Newton's second law. d. Use Newton's first law.