Physics 7. Homework # 3
Due:
4/19
1) According to Galileo, would a
Martian astronomer looking at the Earth find that our planet
a) Is stationary
b) Moves around Mars
c) Exhibits phases like Venus
d) Does not exhibit phases like
Venus
2) Two
spaceships, labeled L and R, pass each other. An astronaut in L claims that R
moves to the right at 1,000 km/s,
a) Then R will claim that L moves
left at 1,000 km/s, and they are both right since only relative motion is significant
b) Then R will find that L is
stationary
c) Then R will claim that L moves
left at 1,000 km/s, and they are both wrong since one can only measure velocity with
respect to a stationary object like the Earth
d) The whole statement is
inconsistent since in space there is no notion of velocity
3) What is an inertial reference
frame?
a) A reference frame glued to the
Earth
b) A reference frame glued to the
center of the universe, which is in absolute rest
c) A reference frame where free
bodies move at constant speed in a straight line
d) A reference frame where free
bodies are uniformly accelerated
4) Imagine that two crates are on
the surface of an icy lake; one crate is twice as heavy as the other. Imagine
now that you kick both crates, one after the other, with the same force, then
a) The heavier crate will move
slower, this is due to
b) They will move at the same speed since they are acted on by the same force
c) The heavier crate does not
move at all, but you will move backwards
d) The crates will move in
opposite directions.