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Homework 5
Chapter 8
Review Questions: 2, 6, 15, 23, 27, 30, 32
Plug and Chug: All of them
Ranking: 4
Exercises: 12, 20, 30, 42, 46, 48, 50, 60
Problems: 2, 4
Chapter 10
Review Questions: 1, 3, 5, 9, 13, 16, 18, 20, 22
Ranking: 2, 4
Exercises: 2, 8, 12, 16, 20, 28, 30, 42, 58, 60
Problems: 2, 4, 6, 8
Problem II: Perform the TensionTorque problem on slide 34 of Lecture Series 1, with a 100kg box sitting
2 meters from the right end of a 6 meter long 20kg platform.
Problem III: Harry wants to be a punter on the football team, so he uses a very precise stop watch to
calculate his hang time. His trial goes awry however, when after punting the ball in an alley, it lands on
the roof of an adjacent building. Predicting this outcome, he has the where withal to stop the stop
watch at the moment that the ball reaches its maximum height. The stopwatch says 2.0 seconds. He
then measures the height of the roof where the ball lands and finds it to be 15.0 meters high. He finds
the horizontal displacement at this point to also be and 15.0 meters (in the xdirection), from where it is
punted. Assume that the ball is kicked from ground level and calculate the following: (Remember, use a
convention and stick by it, i.e. if down vectors are negative up vectors are positive.) (assume g =
10.0m/s
2
)
a)
What is the initial vertical velocity (
°
o
?
) of the football when it leaves Harry’s foot?
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What is the maximum height that the ball reaches?
c)
How long is the ball in the air before it lands on the roof?
d)
What is the initial horizontal velocity (
°
o?
) of the ball when it leaves Harry’s foot?
e)
What is the magnitude (in square root form) of the final velocity vector (
°
±
) and the
tangent (Tan
² = Opposite/Adjacent)
of the angle (with respect to the flat roof of the
building)?

~":1'
144
PART ON E
MECHANICS
Centripetal Force
d
&
23. When you whirl a can at the end of a string in a circular
28. How can gravity be simulated in an orbiting space
path, what is the direction of the force you exert on the can?
station?
o
24. Is it an inward force or an ourward force that is exerted on
the clothes during the spin cycle of an auromatic washing
A
machine?
\ 29. Distinguish berween linear momentum and angular
momentum.
Centrifugal Force
'l
30. What is the law of inertia for rotating sys tems in terms of
~
25. If the string that holds a whirling can in its circular path
angular momentum?
breaks, what kind of force causes it ro move in a straight
line pathcentripetal, centrifugal, or no force? What law
S"',"
«'it
of physics supports your answer?
31. What does it mean ro say that angular momentum is
t
26. If yo u are in a car that rounds a curve, and you are not
conserved?
wearing a seat belt, and you slide across your seat and
32. If a skater who is spinning pulls her arms in so as to
slam against a car door, what kind of force is responsible
reduce her rotational inertia by half, by how much
for your slidecentripetal, centrifugal, or no force? Why
will her angular momentum increase? By how much
is the correct answer "no force"?
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This note was uploaded on 12/04/2011 for the course PHYSICS 1025 taught by Professor Ramos during the Summer '11 term at Miami Dade College, Miami.
 Summer '11
 Ramos
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