Time and Date Stamps (logged): 12:44:20 05-21-2012
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Precalculus II
Principles of Physics (Phy 121) Final Exam
Completely document your work and your reasoning.
You will be graded on your documentation, your reasoning, and the
correctness of your conclusions.
Test should be printed using Internet Explorer. If
printed from different browser check to be sure test items have not been cut off. If
items are cut off then print in Landscape Mode (choose File, Print, click on Properties
and check the box next to Landscape, etc.).
Name and Signature of Student
_____________________________
Signed by Attendant, with Current Date and Time:
______________________
If picture ID has been matched with student and name as
given above, Attendant please sign here: _________
Instructions:
- Test is to be taken without reference to text or
outside notes.
- Graphing Calculator is allowed, as is blank paper or
testing center paper.
- No time limit but test is to be taken in one
sitting.
- Please place completed test in Dave Smith's folder,
OR mail to Dave Smith, Science and Engineering, Va. Highlands CC, Abingdon, Va.,
24212-0828 OR email copy of document to dsmith@vhcc.edu,
OR fax to 276-739-2590. Test must be returned by individual or agency supervising test. Test is not to be returned to student after it has been taken. Student may, if proctor deems it feasible, make and retain a copy of the test..
Directions for Student:
- Completely document your work.
- Numerical answers should be correct to 3 significant
figures. You may round off given numerical information to a precision consistent
with this standard.
- Undocumented and unjustified answers may be counted
wrong, and in the case of two-choice or limited-choice answers (e.g., true-false or
yes-no) will be counted wrong. Undocumented and unjustified answers, if wrong, never get
partial credit. So show your work and explain your reasoning.
- Due to a scanner malfunction and other errors some
test items may be hard to read, incomplete or even illegible. If this is judged by
the instructor to be the case you will not be penalized for these items, but if you
complete them and if they help your grade they will be counted. Therefore it is to
your advantage to attempt to complete them, if necessary sensibly filling in any
questionable parts.
- Please write on one side of paper only, and staple
test pages together.
Test Problems:
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Problem Number 1
The gravitational effect of the Earth can be
thought of as being spread out over larger and larger spheres, each concentric with the
Earth. The greater the area over which the field is spread, the less the strength of the
field.
At the radius of the Earth, the field strength is
9.8 m/s ^ 2.
- What would be the field strength at twice the radius
of the Earth?
- What would the strength be at 4 times the radius of
the Earth?
- If the radius of the Earth is 6400 km, then what
would be the strength at a distance of `a kilometers from its center?
- At what distance from its center does the
gravitational field of the Earth fall to half its value at the surface?
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Problem Number 2
A series of 3 concentric massless hoops are
constrained to rotate together about an axis which passes through their common center and
which lies perpendicular to their common plane. The first hoop has radius 9.899 meters, the
second a radius of 19.798 meters and the third a radius of 29.697 meters.
Masses of 8 kilograms are attached to each hoop,
with masses separated by `pi / 2.474 meters of arc length along the circumference of each
hoop.
- If a torque of 1730 meter Newtons is applied, what
will be the angular acceleration?
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Problem Number 3
A dirigible, initially stationary within its reference frame, is being pushed by
the wind and also by its propellers. The wind pushes with a force of 2.9 pounds to
the North and the second with a force of 6.71 pounds to the East. The dirigible
starts to move in response to the combined force.
- At what angle with the Easterly direction does the dirigible initially move?
- How many pounds of force does the dirigible experience from the combined effects
of the two forces?
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Problem Number 4
A net force of 1968 Newtons is applied to an object of mass 16 kg for 4 seconds.
Find its change in velocity using Newton's Second Law and your knowledge of uniformly
accelerated motion, and also using the Impulse-Momentum Theorem.
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Problem Number 5
Find the x and y coordinates of an object's
position at t = 1/12 ( 7.5) seconds and at t = 5/8( 7.5) seconds, given that at t =
0 seconds its angular position is 0 radians, and that it moves at constant angular
velocity around a circle of radius 6.8 meters, making a revolution every 7.5
seconds.
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Problem Number 6
What is the mass in kilograms of an object if, when suspended from an ideal
spring whose restoring force constant is 60 Newtons/meter, the mass oscillates at .5555
cycles/sec.
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Problem Number 7
A tower begins at the surface of the Earth, at a distance of 6400 km from the center,
and rises to a position 3000 kilometers further from the center. A person of mass 77 kg
climbs the tower. The individual has an average power output of .55 watts / kg of
body mass, and can sustain this output for 8 hours daily.
- Approximate the work done against gravity for each of the first three 1000
kilometer segments of the tower.
- How many days would be required to make the 3000 kilometer climb?
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Problem Number 8
If a displacement vector has x and y components 3.7
meters and 3.3 meters, respectively, the what are the magnitude and angle the
displacement?
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Problem Number 9
An object, initially at rest, is acted upon by a net force of 293.4 Newtons.
- The object has mass 18 kilograms.
- During the first 2 seconds, based on its velocity
change, by how much will its KE increase?
- During the first 2 seconds, based on the distance
it travels, how much work is done by the net force on the object?
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Problem Number 10
What is the velocity of an object of mass 7 kg if its momentum is known to be
-63 kg m/s?
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Problem Number 11
During 1 second, the velocity of an object
increases by 45 meters/second.
- It is known that the velocity of the object will
eventually increase by 8 meters/second.
- If the rate remains constant, how many seconds
will be required?
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Problem Number 12
An object of mass 9.99 kg sits on a spinning disk at
a point 9 meters from the center of the disk.
- What must be its centripetal acceleration toward the
center of the disk if, due to the rotation of the disk, it is moving at 28.99 meters per
second?
- How much force must be exerted between the object
and the disk to keep the object moving in a circle rather than sliding off the disk?
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Problem Number 13
A mass of 25 kg slides up a
frictionless incline until it is 1.1 meters higher than it was when it started.
- At some point the mass is 'caught'
by an ideal spring at its equilibrium point, which it stretches .63 meters from its
equilibrium length.
- At this position the spring exerts
a force of 653.1 Newtons on the mass.
If the system is released from
rest at this position, the
- How much KE will the system gain
by the time it returns to its equilibrium position?
- How does this example illustrate
the nature of a conservative force?
Assume that as the object returns
to its original position the spring releases the object when the spring is at its
equilibrium position.
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Problem Number 14
A rubber band does 56 J of work
as it launches a mass of 4.5 kg.
- By how much does the elastic PE of
the system change, and if no energy is dissipated what will be the KE change of the mass?
- Assuming that no other forces act
on the mass, if the mass started from rest, what velocity will attain?
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Problem Number 15
If velocity increases linearly from 8 meters per second to 11 meters per second in 6
seconds, then on the average, by how many meters per second does velocity increase per
second?