Ch5 HW3 (Homework)
Arthur Barfield
PHYS 2211, section M, Fall 2008
Instructor: Jennifer Curtis
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Assign
Current Score:
26 out of 26
Due:
Friday, October 3, 2008 09:00 AM EDT
Description
The Energy Principle: Change of identity; Work done by nonconstant forces
Instructions
Reading: Sections 5.55.7
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1. [MI2 05.X.22]
2/2 points
You push a box out of a carpeted room and along a hallway with a waxed linoleum floor. While
pushing the crate
2
m out of the room you exert a force of
29
N; while pushing it
4
m along the
hallway you exert a force of
10
N. To bring it to a stop you exert a force of
5
N through a
distance of
1.1
m, opposite to the motion. How much work do you do in all?
92.5
92.5
J
Solution or Explanation
W
=
1
·
1
+
2
·
2
+
3
·
3
Be careful about signs:
3
·
3
=
F
x
3
x
3
is
negative
, since the force has a negative x
component.
2. [MI2e 5.P.61]
4/4 points
A crate with a mass of
110
kg glides through a space station with a speed of
4.5
m/s. An
astronaut speeds it up by pushing on it from behind with a force of
250
N, continually pushing
with this force through a distance of
8
m. The astronaut moves around to the front of the crate
and slows the crate down by pushing backwards with a force of
220
N, backing up through a
distance of
7
m.
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View Full DocumentWhat is the total amount of work done by the astronaut in these two maneuvers?
W
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 Spring '09
 Kindermann
 Current, Energy, Force, Kinetic Energy, Mass, Potential Energy, Work, Photon, Arthur Barfield PHYS

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