Physics 7. Homework # 2

Due: 4/12

1)      If the Earth is rotating (and the sun is not) the speed at the Earth’s equator is about 1000m/hr, but there are no thousand mile-per-hour winds at the equator because

a)      The atmosphere rotates with the Earth

b)      Gravity does not pull on the atmosphere so it just stays put

c)      There are such winds, but only at the North and South poles

d)     The solar attraction produces an equal and opposite wind

2)      Tycho Brahe observed a supernova in 1572 and he determined that it was located farther than the Moon. This was  contrary to the Aristotelian view of the world because

a)      This same star had already exploded once in the past, as observed by Chinese astronomers in1066 A.D.

b)      It was located very close to the sun and yet it did not destroy it

c)      It represented a change in the celestial region where all objects were supposed to be prefect and hence unchanging

d)     It showed that the Earth was round

3)      Why were epicycles invented?

a)      To hide the true motion of the star from people uninitiated in astronomy

b)      To properly describe the retrograde motion of some planets, especially Mars

c)      To explain why objects fall towards the Earth

d)     To explain why celestial objects move around the Earth

4)      Suppose you have a compact cluster of 10,000 stars, and imagine that outside this cluster there is one other star. What would Kepler predict about the motion of this star and others like it?

a)      That it would fall towards Earth and start moving around it

b)      That it would fall towards our Sun and start moving around it

c)      That is would be completely stationary

d)     That it would circle the cluster and in doing so it obeys the laws of planetary motion