# Unit 5: End of Unit Exam

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Brief summary of Unit Five:

In this unit we learned how to apply Newton's laws of motion to rockets in orbit around a planet and far away from a planet. We ended with a discussion of how a rocket can change orbits.

Before you go to the quiz, see how you do on these two questions. If you have trouble, you might want to review the unit, send a question to the discussion group, or seek help from the instructor.

Practice Question One

Name two factors that you need to consider for motion near the Earth's surface but that you can ignore in an orbit around the Earth.

Practice Question Two

Suppose you are in a circular orbit around the Earth in the Space Shuttle. The nose of the craft is aimed in the direction of motion. You briefly turn on your thrusters. What happens to your orbit?

a. nothing
b. it gets smaller and remains circular
c. it gets larger and remains circular
d. it gets smaller and more elliptical
e. it gets larger and more elliptical

You will get instant feedback on your score on Quiz Five (and your instructor will also be informed of your score). If your score is OK, you may proceed directly to the Essay Question Four on Blackboard. Otherwise, you might want to look at what you missed, ask your instructor about questions you missed, or review relevant parts of the unit.

Essay Question

A baseball game in space. Taking a break from assembling the space station, a bunch of astronauts decide to try playing baseball. They put on their spacesuits and jetpacks and go "outside" to play. In each part, when I say "what happens to ..." I mean does he or it start or stop moving? How fast and in what direction? In each case explain how you know the answer to the question.
A. After each of the players has found a good spot and used his jetpack to stop moving relative to the space station, the pitcher revs up and throws what on Earth would be a good curve ball. What happens to the ball in space? What happens to the pitcher? Assume the ball has a mass of 0.1 kg, the pitcher has a mass (in his suit) of about 100 kg, and he pitches with a speed of 10m/s.
B. The batter takes a crack at the ball and connects; the ball heads back the way it came at about twice the speed it had when it arrived. What happens to the batter?
C. The ball heads straight out into left field, where another astronaut catches it. What happens to him?
D. Would any of these answers be different if they were playing inside the space ship and without their space suits? Explain.

Don't forget to contribute to the discussion on Blackboard on one of the topics in this unit!