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Unformatted text preview: SOLUTION 3 Total grade: [100 PH 1110 Summary Homework 2, A Term 2007 Name Section Number This assignment is worth 2.5% of your ﬁnal grade and is our recommended means for you to assess
your readiness for Exam 2. It is due in conference on Tuesday, September 11th and will be returned
to you in conference on Thursday, September 13‘”, the day before Exam 2. Please show your work
and report your answers to no more than three signiﬁcant ﬁgures. la. [10 pts] You want to reenact Galileo’s famous experiments with gravity. Instead of tossing masses of
different sizes and weights, you use rotten tomatoes. You ﬁnd a way onto the roof of Olin Hall, above
a section of lawn. You realize that the tomatoes will make more dramatic splats if you were to throw
them onto the concrete walk a few meters away from the base of the building. For an initial height h =
19.6 m, and a minimum horizontal travel distance ofxmin = 5.00 In, what minimum horizontal speed
vxm‘“ should you give a tomato for it to land on the concrete? You launch the tomato in the horizontal
direction. Please write your answer in the box. 2
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X“ 3’ = vow/C 3 Va (L) Wm": Vex : 2_ 30 m/s 1b. [10 pts] Then you realize that you could inspire more awe in passers—by if you were to launch a tomato at an angle 45“ above the horizontal. What minimum horizontal speed vx is necessary now?
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1 . ' Points earned on this page: [:l Summary Homework 2, continued. Name Section Number 2a. [10 pts] A car of mass m traveling at a constant speed v slides on an icy patch of road (no friction)
where the road curves in a halfcircle with a radius r. The road is banked at an unknown angle 6. The
car slides neither up nor down the bank throughout the turn. Draw on the sketch below the vectors
representing the forces acting on the car (represented by the rectangle) and label them. Side view ofcar onabanked curve 7 i
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bi g’It’f’ “Sine z m /n 2b. [1 0 pts] Write out Newton’s Second Law for each of the directions indicated by the coordinate
system. ’1 2c. [10 pts] Solve for the unknown angle 6, and write your answer in the box below. ’anm’) N211? Sine €36 } A,
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2 _ I Points earned on this page:_: _‘\ We. Summary Homework 2, continued. Name Section Number 33. [10 pts] In Lab 3 you measured how your effective weight changed as you moved your forearms
while you stood on the force plate. Below are rectangles representing your forearms, the entire rest of
your body, and the force plate. Please draw vectors representing the forces acting on them. Assume
that your arms were positioned symmetrically, such that all horizontal forces cancel. In other words,
you need to draw vectors only up or down. Clearly label each force using the form FA on B, where “A on B” means Object A acting on Object B. Forearms Body Force plate 3b. [10 pts] Now please draw sketches of the reaction forces to each force drawn above, also using the
form FA on 3. Alternatively, you are allowed to describe the reaction forces in complete sentences. ’“5 ’HA‘L Sww‘l‘kwh'bww’k ~Gsv~p£ 0’: M EC>‘)J(\’\ M eru. acres/U3] afﬁx
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30 Summary Homework 2, continued. ___ Section Naming _, 3a. [10 pts] In Lab 3 you measutednhewyont effeCIive weight changed asyou moved your foreanns___.,
whileyou stood 0n the force plate. Beloware rectangles representin'g._youg forearms, the lentile rest of
your body, and the force plate Pleasedraw vectors representing the fotces acting on them.,Assnme
thatyour arms were positioned symmetrically, sychthat all horizontal forces cancel. In'other words,
you need to draw vectors only up or down. Clearly label each force using the fonn'FA on B, where “A
on B” eans Object A acting on Object B. F564 “ﬁnality F or’eanns Body Force plate * 3b. [10 pts] Now please draw sketches of the reaction gorces to each force drawn above, also using the
form‘FA on 3. Alternatively, you e allovfed to describe the reaction forces in complete sentences. Summary Homework 2, continued. Name Section Number 4a. [10 pts] In Lab 4, the masses and hanger are connected to the cart by a string, just as in the picture in
the overview of the lab instructions, or as in the sketch on the left below. Please draw vectors
representing the forces acting on of the masscs and hanger (nth), as well as the cart on the steeply
sloped track (me), making sure to label the forces clearly. T ‘Y N R T“ _ E 5; M M Experimental setup Masses and hanger Cart at rest and in equilibrium 4b. [10 pts] Then based on these freebody diagrams, write out Newton’s Second Law for equilibrium of
the hanger, and equilibrium of the cart along and perpendicular to the track. Indicate the coordinate
systems that you use with clearly labeled vectors near the diagrams above. 40. [I 0 pts] Use the above equations to solve for the magnitude of the friction force, eliminatingthe variable that represents tension in the string. Place your answer in the box below
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4 Points earned on this page: S ...
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 Fall '08
 Kiel
 Force, pts, force plate, Summary Homework

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