Homework #09

# Homework #09 - 1. 3/3 points An electron has mass 9e-31 kg....

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1. 3/3 points An electron has mass 9e-31 kg. If the electron 's speed | | is 0.977 c (that is, | |/ c = 0.977 ), what are the following values? total energy ("particle energy") = 3.7985e-13 3.80e-13 J rest energy = 8.1e-14 8.10e-14 J kinetic energy = 2.9885e-13 2.99e-13 J 2. 1/1 points A baseball of mass 146 g is thrown with a velocity of < 25 , 16 , -11 > m/s. What is the kinetic energy of the baseball? (_) (_) < 45.6, 18.7, 8.8 > J (_) (_) 4.6 J (_) (_) < 3.7, 2.3, -1.6 > J (o) (o) 73.1 J (_) (_) 73100 J 3. 4/4 points The point of this question is to compare rest energy and kinetic energy at high speeds. An alpha particle (a helium nucleus) is moving at a speed of 0.9985 times the speed of light. Its mass is (6.40 10 -27 kg). (a) What is its rest energy? 5.76e-10 5.76e-10 J (b) Is it okay to calculate its kinetic energy using the formula ? (_) (_) Yes, because . (_) (_) Yes, because the formula for kinetic energy is always correct. (o) (o) No, because this formula isn't valid for speeds near the speed of light. (c) What is its kinetic energy? 9.9442e-9 9.94e-09 J (d) Which is true? (_) (_) The kinetic energy is much smaller than the rest energy. (o) (o) The kinetic energy is much bigger than the rest energy. (_) (_) The kinetic energy is approximately equal to the rest energy.

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## This note was uploaded on 04/17/2008 for the course PHYS 172 taught by Professor ? during the Spring '08 term at Purdue University-West Lafayette.

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Homework #09 - 1. 3/3 points An electron has mass 9e-31 kg....

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