Ch5 HW1 S2008

Ch5 HW1 S2008 - Ch5 HW1 S2008 10:28 AM Web Assign Ch5 HW1...

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4/25/08 10:28 AM Ch5 HW1 S2008 Page 1 of 6 http:[email protected][email protected] Ch5 HW1 S2008 (Homework) KRISTIN SEILOFF Instructor: Jennifer Curtis Description Particle energy, rest energy, kinetic energy Instructions Reading: Sections 5.1-5.2 Web Assign Current Score: 22 out of 28 Due: Monday, February 18, 200812:00 PM EST 1. 4/4 points | 1/4 submissions An electron has mass 9e-31 kg. If the electron 's speed | | is 0.918 c (that is, | |/ c = 0.918 ), what are the following values? total energy ("particle energy") = 2.042e-13 2.04e-13 J rest energy = 8.1e-14 8.10e-14 J kinetic energy = 1.232e-13 1.23e-13 J Solution or Explanation The particle energy is The rest energy is The kinetic energy is the particle energy minus the rest energy: . 2. 2/2 points | 2/4 submissions A runner whose mass is 50 kg runs in the +x direction at a speed of 7 m/s. What is the kinetic energy of the runner? K = 1225 1220 J The runner turns around and runs in the -x direction at the same speed. Now what is the kinetic energy of the runner?

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4/25/08 10:28 AM Ch5 HW1 S2008 Page 2 of 6 http:[email protected][email protected] K = 1225 1220 J 3. 1/1 points | 3/4 submissions A baseball of mass 146 g is thrown with a velocity of < 22 , 21 , -14 > m/s. What is the kinetic energy of the baseball? (o) (o) 81.8 J (_) (_) < 35.3, 32.2, 14.3 > J (_) (_) < 3.2, 3.1, -2.0 > J (_) (_) 4.9 J (_) (_) 81800 J 4. 0/1 points | 4/4 submissions One mole of helium atoms has a mass of 4 grams. If a helium atom in a balloon has a kinetic energy of 2.457e-21 J, what is the speed of the helium atom? (The speed is much lower than the speed of light.) v = 27.194 850 m/s 5. 1/1 points | 1/4 submissions You throw a ball of mass 190 g upward. When the ball is 2 m above the ground, headed upward (the initial state), its speed is 18 m/s. Later, when the ball is again 2 m above the ground, this time headed downward (the final state), its speed is 18 m/s. What is the change in the kinetic energy of the ball from initial to final state?
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Ch5 HW1 S2008 - Ch5 HW1 S2008 10:28 AM Web Assign Ch5 HW1...

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