We see other galaxies moving away from us because:
a) We are at the center of an ancient explosion called the big bang that sent matter hurtling through space in all directions.
b) Space itself is expanding so that observers in any galaxy see other galaxies moving away from them.
c) Other galaxies are repelled by the black hole at the center of ours.
b) Space itself is expanding so that observers in any galaxy see other galaxies moving away from them.
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Suppose we want a satellite to revolve around the earth 5 times a day. What should be the radius of its orbit? (The mass of the earth is 5.97 × 1024 kg, G = 6.67 × 10-11 N • m2/kg2, and you can neglect the presence of the moon.)
A) 1.44 × 107 m B) 0.690 × 107 m C) 7.22 × 107 m D) 2.11 × 107 m
A bullet fired horizontally hits the ground in 0.5 s. If it had been fired with twice the velocity it would have hit the ground in
A) less than 0.5 s. B) more than 0.5 s. C) 0.5 s.
You are holding your physics book, pushing upwards on it with the palm of your hand. The reaction to this force is the force on __________ by __________
Fill in the blank(s) with correct word
Photons of red light cause a surface to emit photoelectrons with maximum kinetic energy K(red). If photons of blue light of the same intensity are now used in the experiment, which of the following statements is true about the photoelectrons emitted (if any are emitted)?
A. no photoelectrons are emitted B. maximum K(blue) < K(red) C. maximum K(blue) = K(red) D. maximum K(blue) > K(red) E. none of these choices are true