Author Question: An ancient rock is found to contain 40Ar gas, indicating that 77 of the 40K in the rock has decayed ... (Read 77 times)

cabate · **on:** Jul 29, 2018

An ancient rock is found to contain 40Ar gas, indicating that 77 of the 40K in the rock has decayed since the rock solidified. Any argon would have boiled out of liquid rock. The half-life of 40K is 1.25 billion years.

How long ago did the rock solidify? A) 2.6 billion years
B) 0.50 billion years
C) 1.8 billion years
D) 0.30 billion years

Question 2

What is the minimum energy needed to change the speed of a 1600-kg sport utility vehicle from 15.0 m/s to 40.0 m/s?

A) 1.10 MJ
B) 10.0 kJ
C) 20.0 kJ
D) 40.0 kJ
E) 0.960 MJ