The motion of a particle connected to a spring is described by x = 10 sin (?t). At what time (in s) is the potential energy equal to the kinetic energy?
a. 0
b. 0.25
c. 0.50
d. 0.79
e. 1.0
b
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Mars has a sufficient mass and a low enough temperature that water molecules could exist in its atmosphere as vapor. One reason Mars's atmosphere does not contain a significant amount of water vapor is that
a. Mars formed in a part of the solar nebula that lacked oxygen. b. Mars formed in a part of the solar nebula that lacked hydrogen. c. all of the water vapor was released in the impact that formed Deimos. d. ultraviolet radiation breaks the water molecule into less massive particles that can escape. e. the water molecule combines readily with chlorine to form hydrochloric acid.
Melanie says that when a diver enters an underwater cave of height y, the pressure on her is no greater than ?Wgy. Rosalind says that if the bottom of the cave is a distance Y below the water surface, the pressure on the soles of the diver's feet can reach ?WgY. Which one, if either, is correct? (The density of water is ?W.)
a. Melanie, because the roof of the cave absorbs the water pressure from above. b. Melanie, because only the fluid directly above any volume of the fluid can contribute to the pressure on that volume. c. Rosalind, because a fluid exerts equal pressure in all directions at a given depth. d. Rosalind, because the pressure also depends on ?c, density of the material above the cave roof, so that p = ?cg(Y ? y) + ?Wgy. e. Melanie, because the pressure equals p = ?WgH ? ?cg(H ? h).
Two long parallel wires placed side-by-side on a horizontal table carry identical current straight toward you. From your point of view, the magnetic field at the point exactly between the two wires
A) points up. B) points down. C) points toward you. D) points away from you. E) is zero.
Ten kilograms of water at 0°C is mixed with 10 kg of water at 100°C. What is the change in entropy (in cal/K) of the system?
a. 1000 b. 480 c. ?720 d. 240 e. ?168