Calculate the percentage abundance of 235U and 238U2.0 billion years ago if the abundance today is 0.72%and 99.3%, respectively. The higher percentage of235U probably allowed natural nuclear reactors to occur.Explain why such a reaction could not occurtoday.

tran (mmt2449) – Homework 04 – yao – (56695) 1 This print-out should have 26 questions. v 2 L = 0 Multiple-choice questions may continue on 2▯g the next column or page – ﬁnd all choices before answering. So the distance is proportional to the square of the initial speed. 001 10.0 points A 3.14 g bullet moving at 388 m/s penetrates 003 10.0 points Karen has a mass of 52.7 kg as she rides a tree to a depth of 6.28 cm. Use energy considerations to ﬁnd the aver- the up escalator at Woodley Park Station of age frictional force that stops the bullet. the Washington D.C. Metro. Karen rode a distance of 53.4 m, the longest escalator in Correct answer: 3763.6 N. the free world. 2 The acceleration of gravity is 9.8 m/s . Explanation: How much work did the escalator do on Applying the work-energy theorem, ◦ Karen if it has an inclination of 27.7 ▯ W f ∆K = f ·▯ s = −f s Correct answer: 12819.9 J. 1 0 − mv = −f s Explanation: 2 mv 2