Subject: basic5 From: Lawrence Rudnick Date: Tue, 27 Sep 2005 14:35:42 -0500
 To: Lawrence Rudnick

1. The difference between speed and velocity is that ______.

Correct. Velocity describes speed in a particular direction.

2. The acceleration of gravity on Earth is approximately 10 m/s2 (more precisely, 9.8 m/s2). If you drop a rock from a tall building, about how fast will it be falling after 3 seconds?

This answer does not have units of speed.

3. Suppose you lived on the Moon. Which of the following would be true?

Incorrect.

4. In which of the following cases would you feel weightless?

Your weight would be reduced when the elevator accelerates downward, but you would not be weightless unless the cable broke and you were in free-fall.

5. Which statement must be true in order for a rocket to travel from Earth to another planet?

Correct.

6. Momentum is defined as ______.

Sorry.

7. Which of the following statements is NOT one of Newton's Laws of Motion?

 Your Answer: For any force, there always is an equal and opposite reaction force. Correct Answer: What goes up must come down.
This is Newton's third law of motion, but the question asked for a statement that is NOT one of Newton's laws.

8. Newton's Second Law of Motion tells us that the net force applied to an object equals its:

Sorry.

9. When a spinning ice skater pulls in his arms, he spins faster because ______.

 Your Answer: his angular momentum must be conserved, so reducing his radius must increase his speed of rotation.
Correct.

10. According to the universal law of gravitation, if you triple the distance between two objects, then the gravitational force between them will ______.

Sorry.

11. What is the difference between a bound orbit and an unbound orbit around the Sun?

 Your Answer: An object on a bound orbit follows the same path around the Sun over and over, while an object on an unbound orbit approaches the Sun just once and then never returns.
Correct.

12. Why is Newton's version of Kepler's third law so useful to astronomers?

 Your Answer: It can be used to determine the masses of many distant objects.
Correct.

13. Approximately where is it currently high tide on Earth?

 Your Answer: Anywhere that ocean water laps upon the shore. Correct Answer: On the portions of the Earth facing directly toward the Moon and on the portion of the Earth facing directly away from the Moon.
Sorry.

14. Which of the following facts CANNOT be traced to effects of tidal friction?

True, but this is a result of the Earth's current rate of rotation, not of tidal friction (although the rate of rotation has been affected by tidal friction over billions of years.

15. If the Moon did not have a synchronous rotation, then

 Your Answer: we would no longer have tides on Earth. Correct Answer: we would no longer always see nearly the same face of the Moon.
Tides would still be produced by the Moon.

16. Suppose that a lone asteroid happens to be passing Jupiter on an unbound orbit that keeps it well above Jupiter's atmosphere and far from all of Jupiter's moons. Which of the following statements would be true?

 Your Answer: The asteroid's orbit around Jupiter would not change, and it would go out on the same unbound orbit that it came in on.
Correct. Orbits cannot change spontaneously.

17. Newton showed that Kepler's laws are ______.