Question

1-Why doesn't the force of gravity change the speed of a satellite in circular orbit?

2-A circularly moving object requires a centripetal force. What supplies this force for satellites that orbit the Earth?

3-A 'geosynchronous' Earth satellite can remain nearly directly overhead in Singapore, but not in San Francisco. Why?

4-True or false: For orbits of greater altitude, the period is longer.

5- Fill in the blank:

____(a)______gathered the data that were used to show that the planets travel in elliptical orbits around the sun___(b)_______discovered the orbits were elliptical.______(c)_______explained them.

Answer 1

(1)

A satellite in circular orbit has a constant gravity force on it. This force is always at right angles to the motion of satellite, so it can't change the speed. You need a force in the direction of motion to change the speed.

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(2) Gravity supplies the necessary centripetal force to hold a satellite in orbit about the earth.

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(3)

A geosynchronous satellite orbits above the equator. Singapore is on equator, but the other cities are not.

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(4) True, because of the distances involved at higher and higher altitudes

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(5)

(a) Scientists (b) Kepler (c) Kepler