Physics 7 (Winter 08) – Homework #3

Due: 1/29

 

  1. How did Copernicus explain the retrograde motion of mars?
  2. John the engineer is on a very big spaceship and, looking out a window, he sees Mary (an astronomer) traveling to his left in a very small spaceship. Mary sees John and his ship move in the opposite direction. Who is right?
    1. John because his ship is so big it is necessarily at rest
    2. Mary because astronomers are more reliable than engineers
    3. Both are wrong since their observations are contradictory: John sees himself at rest and Mary moving, Mary sees herself at rest and John moving!
    4. Both are right since speed depends on the frame of reference
  3. A rocket takes off from a space station, and after a few minutes turns off its rockets, then
    1. Its acceleration is not zero only while the rockets are on
    2. Its velocity with respect to the station is always zero
    3. Its acceleration is always zero
    4. Its acceleration is never zero
    5. Its velocity will slowly drop to zero after the rockets are turned off
  4. Jupiter’s moons provided support for the heliocentric hypothesis because
    1. They orbited Jupiter and not the Earth
    2. They were made of earthy stuff and yet they did not fall towards the Earth
    3. According to Aristotle such bodies could not exist
    4. Their existence was predicted by Copernicus
    5. They were made of fiery stuff and yet did not move continuously away from Earth
  5. An accelerating spaceship in outer space receives a very heavy cargo load, assuming that this does not affect the thrust of its rockets
    1. There will be no change in the motion of the spaceship
    2. The spaceship will increase its acceleration
    3. The  spaceship will decrease its velocity but increase its acceleration
    4. The spaceship will decrease its acceleration
    5. The spaceship will increase both its velocity and its acceleration
  6. When a feather and an anvil fall from the same height the feather hits the ground last because
    1. The feather is more fiery than the anvil
    2. The air resistance forces are stronger on the feather
    3. Gravity is weaker on the feather
    4. The anvil is more earthy than the feather
    5. Gravity acts stronger on the anvil
  7. When white light goes through a prism it produces a rainbow of colors. This implies that
    1. White light cannot be decomposed
    2. Light moves with infinite speed
    3. Light breaks the atoms in the prism
    4. White light is composed of a variety of colors
    5. Any light of a single color can be transformed into white light
  8. A man is standing on the Earth’s equator, then
    1. He is not accelerating since his speed is zero
    2. He cannot determine whether he is accelerating or not since acceleration is relative to the observer reference frame
    3. He is accelerating
    4. He is not accelerating since he is moving at constant speed in a straight line
    5. He is moving at constant absolute velocity in contradiction to Galileo’s principle of relativity
  9. An ice skater pushes off the side of the rink and, without moving her legs, slides towards the other side.  This is because
    1. Horizontal motion is natural
    2. Her motion is free of external influences and so she’ll continue her state of motion at constant speed in a straight line
    3. There is a force pulling at her from the other side of the rink
    4. There is a force repelling her from the side of the rink she started from
    5. The frictional forces on ice impel her
  10. Suppose the universe is infinite, and is filled with an infinite number of stars. Imagine now that on September 1st at midnight the speed of light changes form its current value and becomes infinite, the night sky
    1. Will continue looking more or less the same as before
    2. Will look increasingly darker until it becomes completely black
    3. Will look increasingly brighter, but after a while it will become dark again
    4. Will brighten somewhat and then stop changing
    5. Will become infinitely bright