Time and Date Stamps (logged): 01:47:07 08-29-2008
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Precalculus II
Principles of Physics (Phy 121) Test_1
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 momentum of an object is 36 kg m/s. How fast is it moving if its mass is 6
kg?
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Problem Number 2
An object whose mass is 91 kilograms is accelerated from rest to 14 meters/second over
an unspecified time interval. It continues accelerating at the same average rate for an
equal time interval. The result is that its previous velocity is doubled.
- What will be the kinetic energy after the first time interval?
- What will be the kinetic energy after the second time interval?
- How many times as much kinetic energy does the object have after the
second time interval, compared with the kinetic energy at the end of the first time
interval?
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Problem Number 3
What are the x and y components of a vector whose
length is 2 and whose angle with the positive x axis is 209 degrees?
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Problem Number 4
Problem: What are x and y the components of the
force vector obtained when we add the two following force vectors:
- vector A, with x and y components 8.5 Newtons and
-1.3 Newtons, and
- vector B whose x and y components are -4.1 Newtons
and -4.8 Newtons?
What are the magnitude and angle of the resultant
vector?
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Problem Number 5
By how much will the kinetic energy (abbreviated KE) of an object increase as a result
of a net force of 380 Newtons exerted over a distance of 40 meters, assuming (ideally)that
no energy is dissipated in the process?
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Problem Number 6
Two objects collide, one of mass 14 kg and
moving in the positive direction at 26 m/s and the other of mass 11 kg moving at 7 m/s in
the negative direction.
- Assuming that the two objects stick together when
they collide, what then is the total mass and velocity immediately after collision?
The momentum of the first is ( 26 m/s)( 14 kg)= 364
kg m/s, and that of the second is ( - 7 m/s)( 11 kg) = -77 kg m/s.
- The total momentum is therefore 364 kg m/s + `p2 kg
m/s = 287 kg m/s.
- The total mass is easily found to be 25 kg. Since
the total momentum after collision is the same as that before collision, we see that after
collision we have a mass of 25 kg with momentum -77 kg m/s.
- Dividing we obtain velocity ( -77 kg m/s)/( 25 kg) =
11.48 m/s.
The total momentum of a mass m1 moving at velocity
v1 and a mass m2 moving at velocity v2 is
By Newton's Third Law and the Impulse-Momentum
Theorem this momentum will remain unchanged during collision.
After collision we wil have one object of mass m1 +
m2 and momentum m1 v1 + m2 v2. The object will therefore have velocity
velocity = momentum / mass = (m1 v1 + m2
v2) / (m1 + m2).
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Problem Number 7
One object pushes another.
- The pushing object has available a total of 54 Joules of energy.
- It must push the other object at least 3 meters.
- What is the maximum possible constant force parallel to the direction of
motion thatt could be exerted through this distance before using up all its energy?
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Problem Number 8
You and I are pulling on a massive, initially stationary object resting on a
smooth frozen pond. You pull with a force of 2.7 pounds to the North and I pull with
a force of 5.74 pounds to the East. The object starts to move in response to our
combined force.
- At what angle with the Easterly direction does the object initially move?
- How many pounds of force does the object experience from our combined pulls?
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Problem Number 9
An object of mass 13 kg experiences a net force of 1937 Newtons for .02 seconds.
Use Newton's Second Law and your knowledge of uniformly accelerated motion to find its
change in velocity.
Use the Impulse-Momentum Theorem
to obtain the same result.