Potassium-40 decays to argon-40 has a half-life of 1.25 billion years. Suppose you find a rock that has only 1/8 of its original potassium-40 still remaining. How old is the rock?
A) 3.75 billion years
B) 5.25 billion years
C) 2.5 billion years
D) 1.25 billion years
E) 4.5 billion years
A) 3.75 billion years
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The fact that the properties of the Universe are close to the dividing line between open and closed Universes refers to the _______________ problem
Fill in the blank(s) with correct word
Which of the following was not observed by Galileo?
A) phases of Venus B) four moons orbiting Jupiter C) stellar parallax D) mountains and valleys on the Moon
From the edge of a roof top you toss a green ball upwards with initial speed v0 and a blue ball downwards with the same initial speed. Air resistance is negligible. When they reach the ground below
A) the green ball will be moving faster than the blue ball. B) the blue ball will be moving faster than the green ball. C) the two balls will have the same speed.
A stone is held at a height h above the ground. A second stone with four times the mass of the first one is held at the same height. The gravitational potential energy of the second stone compared to that of the first stone is
A) one-fourth as much. B) one-half as much. C) twice as much. D) four times as much. E) the same.