IUPhysicsP201F2009
Assignment 6b
Due at 12:00pm on Sunday, October 19, 2008
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Conservation of Momentum in Two Dimensions Ranking Task
Description:
Conceptual question on conservation of momentum in two dimensions. (ranking task)
Part A
The figures below show bird'seye views of six automobile crashes an instant before they occur. The automobiles
have different masses and incoming velocities as shown. After impact, the automobiles remain joined together and
skid to rest in the direction shown by
. Rank these crashes according to the angle
, measured
counterclockwise as shown, at which the wreckage initially skids.
Rank from largest to smallest. To rank items as equivalent, overlap them.
Hint A.1
Conservation of momentum in two dimensions
Since momentum is a vector quantity, the
x
component of momentum and the
y
component of momentum must be
individually conserved in any collision. Thus, the total
x
momentum before the collision must be equal to the total
x
momentum of the sliding wreckage after the collision. The same is true for the total
y
momentum.
Hint A.2
Determining the angle
Once the
x
and
y
momenta of the wreckage are determined, the exact angle through which the wreckage skids can
be determined by trigonometry. Determining the exact angle of this final momentum vector is accomplished the
same way you would find the angle of any vector, typically by finding the inverse tangent of the
y
component
over the
x
component. (You can also determine the ranking without calculating the exact angle at which the
wreckage skids.)
ANSWER:
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The Center of Mass of the EarthMoonSun System
Description:
Students first calculate the location of the center of mass for the EarthMoon system and then
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MasteringPhysics: Assignment Print View
10/6/2008
http://session.masteringphysics.com/myct/assignmentPrint?assignmentID=1158638
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View Full Documentcalculate the center of mass for the EarthMoonSun system.
A common, though incorrect, statement is, "The Moon orbits the Earth." That creates an image of the Moon’s orbit
that looks like that shown in the figure.
The Earth's gravity pulls on the Moon, causing it to orbit.
However, by Newton’s third law, it is known that the
Moon exerts a force back on the Earth. Therefore, the
Earth should move in response to the Moon. Thus a
more accurate statement is, "The Moon and the Earth
both orbit the center of mass of the EarthMoon system."
In this problem, you will calculate the location of the center of mass for the EarthMoon system, and then you will
calculate the center of mass of the EarthMoonSun system. The mass of the Moon is 7.35×10
22
, the mass of the
Earth is 6.00×10
24
, and the mass of the sun is 2.00×10
30
. The distance between the Moon and the Earth is
3.80×10
5
. The distance between the Earth and the Sun is 1.50×10
8
.
Part A
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 '08
 Bau
 Chemistry, pH, Center Of Mass, Assignment Print View, The Moon

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