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Unformatted text preview: S O LUT! 0N5 Total grade: PH 1110 Summary Homework 2, A Term 2010 Name Section Number This assignment is worth 1.25% of your ﬁnal grade, and it assesses your readiness for Exam 2. It
is due in conference on Tuesday, September 14th and will be returned to you in conference
Thursday, September 16th, the day before Exam 2. Show your work; use the back sides of these
pages if necessary. Answers should be reported to no more than three signiﬁcant digits, as
appropriate. la. [10 pts] In Experiment 3 you used a force plate to measure forces in the vertical direction and made
freebody diagrams based on your experience. Let us now move on to a twodimensional situation.
Below in the left sketch is a toboggan, represented by a rectangle on the right. Two children sit in the
toboggan, which is being pulled by an adult at constant velocity by a rope at an angle 0 up from the
horizontal. The surface is horizontal. Sketch the forces of the freebody diagram of the toboggan.
Clearly label each force using the form FA on B, where “A on B” means Object A acting on Object B.
Please use the abbreviations T = toboggan, C = children, R = rope, E = Earth, and S = snow. .z‘ (W ‘: l1 6 mm
‘ ’ in; M! ‘< Side View of toboggan lb. [10 pts] Now please draw sketches of the reaction forces to each force drawn above, also using the
form FA on B. L:
\ 1 Points earned on this page: Summary Homework 2, continued. Initials Section Number 2a. [5 pts] Experiment 4 can be modiﬁed such that masses on a hanger are connected to the cart by a
string, as in the sketch on the left below. Please draw vectors representing the forces acting on the
masses and hanger, m1], as well as the cart on the steeply sloped track, me, making sure to label the
forces clearly. Denote the tension in the string by T. The system is at rest and friction is negligible. You know the values of ink, mo, and g. P» H, Experimental set—up Masses and hanger Cart 2b. [5 pts] Then based on these free—body diagrams, write out Newton’s Second Law for equilibrium of
the hanger, and equilibrium of the cart along and perpendicular to the track (three equations). Indicate
the coordinate systems that you use with clearly labeled vectors near the diagrams above. k. Em. Z r a. v: 4: r ‘ ‘ Bu »> it
.. RX / ewa 55):; {:9 2 (23¢ ; 6 ﬂ [K ”i ‘~J 543,, :5 r 20. [5 pts] Solve for the unknown angle 9 in terms of the known values, and write your answer in the box
below. , J j 1 Fv‘. 5ft, 12.6w“) in
N L 3 Six in 5T3 2d. [5 pts] For m, = 432 g and me = 543 g, what is the numerical value of 9? Please place your answer in
the box. 2 Points earned on this page: Summary Homework 2, continued. Initials Section Number 3a. [5 pts] In Mastering Physics Assignment 6, Yusef accelerated a chair across a floor, as in the left—
hand sketch below. Let us now examine the few seconds before acceleration, when the chair was in
equilibrium. Please draw vectors representing the forces acting on the chair. Denote the pushing force
exerted by Yusef as FF. The system is at rest and friction is NOT negligible. You know the values of
FF, m, g, and the angle 9 down from the horizontal at which Yusef is pushing. 3b. [5 pts] Then based on these free—body diagrams, write out Newton’s Second Law for equilibrium of
the chair (two equations). Indicate your coordinate systems with clearly labeled vectors near the sketch above. ‘ cl ‘
14v
ﬁatDe ’MM 3 O
Pd»; .
”I” N—m3_F‘Psn/te:0 3c. [5 pts] Solve for the unknown coefficient of friction it in terms of the known variables, and write your
answer in the box below. .
I: 616:: 69 Meiv M a gate
Na) + FF 5M9 3d. [5 pts] For m = 55.0 kg, Fp = 184 N, and B = 35.00, what is the numerical value of u? Please place
your answer in the box. I“ “A? 3‘7 _
5.535533 + [Vislmﬁ’f 44: M: (1234 0.234 M: 3 Points earned on this page: Summary Homework 2, continued. Initials Section Number 4a. [5 pts] A block of mass m accelerates down a slope of angle 9. The coefﬁcient of sliding friction is u.
Draw on the rectangle on the right the vectors representing the forces acting on the block and label
them. Also sketch and label the coordinate system that you will use to write out Newton’ Second
Law. You know the values of m, g, 6, and u. 6 Side View of block on a slope Forces on block 4b. [5 pts] By writing out Newton’s Second Law for the two directions of your coordinate system, ﬁnd
the acceleration a. Express your answer in terms of the known variables m, g, 6, and u. 4c. [5 pts] Find the force F needed to slow the acceleration to zero. Express your answer in terms of the known variables m, g, 9, and u.
«vﬁ ”A. 4d. [5 pts] Of the variables a and F, which is (are) vectors and which scalars? ,7 ,.\ 4 Points earned on this page: 1 Summary Homework 2, continued. Initials Section Number 521. [5 pts] You and your roommate are walking in a park when you see a child’s merry—go—round. Your
roommate, mass m, sits on the edge of the horizontal wheel of radius r while you push it faster and
faster. At an easily measurable speed v, your roommate slips off. Draw the forces acting on your
roommate the instant before slippage. Include a coordinate system. You know the values of m, g, r,
and V. N
a ”d
. 4 %] «:4
W6 Merry—go—round Roommate 5b. [5 pts] Consistent with your free—body diagram and the two directions of your coordinate system,
write out Newton’ 5 Second Law for this problem. “1.2”;
N~Mj : 0
Lu”  Mr:
MN " f; H ll 073% 5d. [5 pts] Solve for the numerical value of the coefficient of friction if m = 65.4 kg, g = 9.80 III/82, r =
1.96 m, and V = 2.31 m/s. ~ (1301 c 02.77 M ._ aw mt
M: 01'377
5 Points earned on this page: [:1 ...
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 Spring '08
 Kiel
 mechanics

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