# Problem Set 6 __25_ by panniuniu

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Name: ______________________________                                              Unit 2 – Gravity and Motion      #25

PROBLEM SET 6
42 pts.
Instructions:     Put your name and final answers ONLY on this sheet. Show all work for each problem on
a separate sheet of notebook paper and staple to the back of this paper prior to
submission. Give all answers using the appropriate number of significant figures unless
otherwise noted and proper scientific notation when necessary. Remember units!

1.   Compared with the strength of Earth’s gravity at its surface, how much weaker is gravity at a
distance of 10 Earth radii from Earth’s center? At 20 Earth radii? (4 pts.)

2.   Find the force of lunar gravity on the surface of the moon then find the of Earth’s gravity at
Earth’s surface. Compare the two values by specifying which is stronger and by how much.
Hint: Use the formula for surface gravity. (5 pts.)

3.   If a small lead ball falls from a high tower on Earth, what will be its velocity after 2 seconds?
After 4 seconds? (2 pts.)

4.   What is the circular velocity of an Earth satellite 1000 km. above the Earth’s surface? Answer in
m/s and with 3 sig figs. Hint: Use the planetary data table to find Earth’s radius. (2 pts.)

5.   What is the circular velocity of an Earth satellite 36,000 km. above Earth’s surface? What is its
orbital period? Answer in m/s for circular velocity and with 3 sig figs and answer in seconds for
the orbital period with 3 sig figs. Hint: Use the planetary data table to find Earth’s radius. (4 pts.)

6.   What is the orbital period of an imaginary satellite orbiting just above Earth’s surface? Ignore
friction with the atmosphere. Answer in minutes and with 3 sig figs. Hint: Use NVK3L. (3 pts.)

7.   Repeat the previous problem for Mercury, Venus, the moon, and Mars. Hint: Find the masses
and radii of these objects using the planetary data table and use NVK3L. (12 pts.)

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8.   If you visited an asteroid 30 km. in radius with a mass of 4.0 x 10 kg, what would be the circular
velocity at its surface? A major league fastball travels about 90 mph. Could a good pitcher,
capable of throwing this velocity, throw a baseball into orbit around the asteroid? Show work for
this portion. Answer in m/s and with 3 sig figs. Hint: There are 3.28 ft in 1 mile. (4 pts.)

9.   What is the orbital period of a satellite orbiting just above the surface of the asteroid in the
previous problem (#8)? Answer in minutes and with 3 sig figs. Hint: Use NVK3L. (2 pts.)

10. What would be the escape velocity at the surface of the asteroid in problem #8? Could a major
league pitcher throw a fastball (90 mph) off of the asteroid? Show work for this portion.
Answer in m/s and with 3 sig figs. (4 pts.)

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