The lifetime of uranium 238 is 6.0 × 109 y, and that of uranium 235 is 1.0 × 109 y. The present abundance of uranium 238 is 140 times the abundance of uranium 235. What was the ratio of abundances 1 billion years ago?
A)
140:1
B)
6:1
C)
61:1
D)
161:1
E)
322:1
C
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Volcanoes that explode violently tend to have magmas of
a. high temperature and low silica content. b. high temperature and high silica content. c. low temperature and low silica content. d. low temperature and high silica content.
Significant Figures: The last page of a book is numbered 764. The book is 3.0 cm thick, not including its covers. What is the average thickness (in centimeters) of a page in the book, rounded to the proper number of significant figures?
A. 0.0039 cm B. 0.072 cm C. 0.0079 cm D. 0.00393 cm E. 0.00785 cm
A 7.5-kg otter slides down a hill, starting from rest at the top. The sloping surface of the hill is 8.8 m long,
and the top is 6.5 m above the base. If the speed of the otter at the bottom of the hill is 9.2 m/s, how much energy of the otter-Earth system was converted to internal energy?
Suppose that a rigid aluminum wire were to be strung out in a loop that just fits snugly around the equator (assuming a perfectly spherical Earth with a radius of 6.37 × 106 m)
If the temperature of the wire is increased by 0.50°C, and the increase in length is distributed equally over the entire length, how far off the ground will the wire loop be if it remained centered on the earth? The coefficient of linear expansion of aluminum is 24 × 10-6 K-1. A) 76 cm B) 760 m C) 76 mm D) 7.6 mm E) 76 m