In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot due to gravitational contraction. What was the major drawback to this idea?
A) It predicted that the Sun would shrink noticeably as we watched it, but the Sun appears to be stable in size.
B) It is physically impossible to generate heat simply by making a star shrink in size.
C) It predicted that the Sun could shine for about 25 million years, but geologists had already found that Earth is much older than this.
D) It predicted that Earth would also shrink in size with time, which would make it impossible to have stable geology on our planet.
C
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Johnny throws a shotput at an angle of 45.° and it travels a horizontal distance of 30. meters. If he releases the shotput at the same speed but changes the angle to 55.°, what will be the new range (distance)?
A) 25. m B) 28. m C) 41. m D) 32. m E) 37. m
The mass of a black hole can be determined by ________.
A. measuring its volume and density B. applying the modified version of Kepler's Third law, if the black hole is in a binary system C. the electromagnetic radiation it emits D. how rapidly it is spinning
Energy Conservation With Conservative Forces: A 5.0-N projectile leaves the ground with a kinetic energy of 220 J. At the highest point in its trajectory, its kinetic energy is 120 J. To what vertical height, relative to its launch point, did it rise if there was no air resistance?
A. 44 m B. 24 m C. 20 m D. 10 m E. It is impossible to determine the height without knowing the angle of launch.
Uniform Circular Motion: When an object moves in uniform circular motion, the direction of its acceleration is
A. in the same direction as its velocity vector. B. in the opposite direction of its velocity vector. C. is directed toward the center of its circular path. D. is directed away from the center of its circular path. E. depends on the speed of the object.