Uranium-238 decays into lead-206 with a half-life of 4.5 billion years. Suppose you found a rock in which only 1/4 of the original uranium-238 remained (the other ¾ having become lead-206). How old would the rock be?

A) 9 billion years
B) 4.5 billion years
C) 2.25 billion years
D) 13.5 billion years


A) 9 billion years

Physics & Space Science

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If the speed of waves traveling along the first wire is 54.0 m/s, what is the speed of waves traveling along the second wire? A) 24.9 m/s B) 27.2 m/s C) 36.2 m/s D) 81.0 m/s E) 100 m/s

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A rad is that amount of radiation that:

a. is also known as a rem. b. deposits 10–2 J of energy into 1 kg of absorbing material. c. deposits 8.76 × 10^–3 J of energy into 1 kg of air. d. produces 2.08 × 10^9 ion pairs per cm3 in air under standard conditions.

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Ideal Gas Law: Your lungs hold 4.2 L of air at a temperature of 27°C and a pressure of 101.3 kPa. How many moles of air do your lungs hold? (R = 8.31 J/mol ? K)

A. 0.15 moles B. 0.17 moles C. 0.19 moles D. 0.21 moles E. 0.23 moles

Physics & Space Science

According to the text’s final model (including the ocean effect), about when will the earth’s average surface temperature be 288.4 K?

A. 2015 B. 2030 C. 2045 D. Some other date (specify)

Physics & Space Science