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Ch5 HW1 S2008
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http://www.webassign.net/v4cgikseiloff3@gatech/student.pl?k=20080425142235kseiloff3@gatech1286165155
Ch5 HW1 S2008 (Homework)
KRISTIN SEILOFF
Instructor: Jennifer Curtis
Description
Particle energy, rest energy, kinetic energy
Instructions
Reading: Sections 5.15.2
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 9e31 kg. If the
electron
's speed 
 is
0.918
c
(that is, 
/
c
=
0.918
), what are the following values?
total energy ("particle energy") = 2.042e13
2.04e13
J
rest energy = 8.1e14
8.10e14
J
kinetic energy = 1.232e13
1.23e13
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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Ch5 HW1 S2008
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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
2.457e21
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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 Spring '06
 SCHATZ
 Physics, Current, Energy, Kinetic Energy, Work

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