When we say that a cluster of galaxies is acting as a gravitational lens, what do we mean?
A) It bends or distorts the light coming from galaxies located behind it.
B) It magnifies the effects of gravity that we see in the cluster.
C) It is an unusually large cluster that has a lot of gravity.
D) The overall shape of the cluster is that of a lens.
A) It bends or distorts the light coming from galaxies located behind it.
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Rotational Kinetic Energy: A solid ball of mass 1.0 kg and radius 10 cm rolls with a forward speed of 10 m/s when it comes to a hill. There is enough friction on the hill to keep the ball from slipping as it rolls up.(a) How high vertically up the hill can the ball roll before coming to rest?(b) How high vertically could the ball go if the hill were totally frictionless?(c) How is it that the ball can go higher with friction than without friction?
What will be an ideal response?
Niobium metal becomes a superconductor (with electrical resistance equal to zero) when cooled below 9 K. If superconductivity is destroyed when the surface magnetic field exceeds 0.100 T, determine the maximum current a 2.00-mm diameter niobium wire can carry and remain superconducting. (µ0 = 4p × 10^-7 T×m/A)
a. 2000 A c. 125 A b. 1000 A d. 500 A
Two ice skaters, one with a mass of 45 kg and the other with a mass of 60 kg, push off against one another starting from a stationary position. After they have pushed off, the relative speed at which they separate is 0.600 m/s. What is the speed of the 60-kg skater?
A) 0.343 m/s B) 0.257 m/s C) 0.375 m/s D) 0.750 m/s E) 0.225 m/s
If an electron moves in a magnetic field,
A. it always feels a force. B. it only feels a force if its velocity vector is parallel (or antiparallel) to the direction of the magnetic field. C. it does not feel a force if it is in motion, only if stationary. D. it only feels a force if its velocity vector is not parallel (or antiparallel) to the direction of the magnetic field.