An 80-kg man is skating northward and happens to suddenly collide with a 20-kg boy who is ice skating toward the east
Immediately after the collision, the man and boy are seen to be moving together at 2.5 m/s in a direction 60° north of east. How fast was the boy moving just before the collision?
6.3 m/s
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Which of the following statements about quantum tunneling is not true?
A) It is used in modern electronics and, in fact, our modern-day computers would not work without it. B) It plays a crucial role in nuclear fusion in the Sun. C) It allows electrons and other subatomic particles to pass through wall-like energy barriers even when it seems they do not have enough energy to get through the barriers. D) Although it has been observed to occur, it violates all other known laws of nature, and explaining it therefore represents a major challenge to physicists.
A ball is projected upward at time t = 0.00 s, from a point on a roof 70 m above the ground and experiences negligible air resistance. The ball rises, then falls and strikes the ground
The initial velocity of the ball is Consider all quantities as positive in the upward direction. The velocity of the ball when it is above the ground is closest to A) -38 m/s. B) -30 m/s. C) -23 m/s. D) -15 m/s. E) -45 m/s.
If both 30-GeV electrons and 30-GeV protons are used to probe the nucleus, which has the shorter wavelength?
A) They are the same. B) the electrons C) the protons D) It depends on the nucleus probed. E) They are never the same.
Suppose that, for some unknown reason, the core of the Sun suddenly became hotter. Which of the following best describes what would happen?
A) Higher temperature would cause the rate of nuclear fusion to rise, which would increase the internal pressure, causing the core to expand and turn the Sun into a giant star. B) Higher temperature would cause the rate of nuclear fusion to rise, which would increase the internal pressure, causing the core to expand and cool until the fusion rate returned to normal. C) Higher temperature would cause the rate of fusion to fall, decreasing the internal pressure and causing the core to collapse until the rate of fusion returned to normal. D) The higher temperature would not affect the fusion rate but would cause the core to expand and cool until the temperature returned to normal, with the core at a new, slightly larger size.