Why are there no impact craters on the surface of Io?
A) It is too small to have been bombarded by planetesimals in the early solar system.
B) Any craters that existed have been eroded through the strong winds on Io's surface.
C) Jupiter's strong gravity attracted the planetesimals more strongly than Io, and thus none landed on its surface.
D) Io did have impact craters, but they have all been buried in lava flows.
E) Io's thick atmosphere obscures the view of the craters.
D
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What will be an ideal response?
A ball drops some distance and loses 30 J of gravitational potential energy. Do NOT ignore air resistance. How much kinetic energy did the ball gain?
A) more than 30 J B) exactly 30 J C) less than 30 J
In a certain region of space there is a uniform magnetic field pointing in the positive z direction (+z). In what direction should a negative point charge move to experience a force in the positive x direction (+x)?
1.in the positive z direction (+z) 2.in the negative z direction (–z) 3.in the positive x direction (+x) 4.in the negative x direction (–x) 5.in the positive y direction (+y) 6.in the negative y direction (–y) 7.It can move in any direction. 8.It is impossible for the force to be in the +x direction when the magnetic field is in the +z direction.
If a quantity is conserved, it means that it
Choose one: A. can be saved for a later time. B. changes only if an external force acts. C. changes only if an internal force acts. D. it doesn't change.