Today, the uranium found on Earth contains 0.720% 235U (with a half-life of 0.700 billion years) and 99.28% 238U
(with a half-life of 4.50 billion years). At a time 2.20 billion years ago, what percent of the uranium on Earth was 238U (assuming that no other uranium isotopes were present)?
A) 8.68% B) 95.6% C) 2.18% D) 4.53% E) 6.29%
B
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In order to remain stable, a star must have an internal balance between
A) gravity and pressure. B) gravity and temperature. C) temperature and pressure. D) pressure and nuclear fusion. E) nuclear fusion and chemical reactions.
A 1.7 H inductor has a current of 6.6 A flowing through it. The current reduces to 3.3 A over a period of 1.6 s. What is the average power the inductor supplies to the circuit as the current reduces?
A. 17 W B. 37 W C. 9.3 W D. 28 W E. 46 W
For lunar tides to occur in the human body,
A) most of the body would have to be in the liquid state. B) Earth's gravitation would have to be incredibly small. C) parts of the body would have to be appreciably closer to the Moon than other parts. D) the body would have to be female, as evidenced by women's monthly menstrual cycles. E) none of these
As a solid is gradually heated, it first glows
A) red. B) yellow. C) white. D) blue.