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Unformatted text preview: Pant ‘ Chapter 7 & 8 — Answers to suggested homework problems m2=18 kg, m3=7.9 kg, m4=23 kg
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Xcm‘ 36M: — QSéM 7—48. A person of mass 90 kg standing on a h bullet of mass 40 g in a horizontal direction. After the bullet has travelled a distance of 50 m, what distance
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8—3. An oldfashioned (vinyl) record rotates at a cons an '. ' ‘  a) What is its’an‘gular velocity in rad/s? (b) lfthe record has a radius of 18 cm, what is the linear speed of a point on its edge? (lﬂf‘ml') A lmm . my” ‘ lr—es/ (79$ (53 vzw r: ('2,crécg~t)(ig%3 Ml 8—5. Consider again the record in Problem 3. if it plays music for 20 miraahow far does a point
on the edge travel in meters? Beau/5Q u.) , is COVKH'oIn’l'i W 6, Cam 14‘va WH’A 4:9 a
w w: 3% a A9: wot am * 4/(20W2(L°s«) 3" IN“ “>09? LHSRWA . New (Age, 533(69 4'0 ‘n’wf g 5: r 9 = (twilasiiww 8—12. An adult is riding on a carousel and finds that he is feeling a bit nauseated. He then
decides to move from the outer edge of the carousel to a point a distance r2 from the center so
that his linear speed is reduced by a factor of 2.5. lfthe carousel has a constant angular velocity of 1.0 rad/s and a radius of 3.3 m, what is r2? Far/g4. “94 e, +1,“ + : V1 , a— "‘ f},3p§w “AA W‘LG (: B€mug€ \/.:/‘C«J WQ (am 5,;L/egpor {‘3‘ I A
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42 Ce :5 819. A rod of length 3.8 m is hinged at one end, and a force of magnitude F: 10 N is applied at
the other (Fig. P8.19). (a) If the magnitude of the torque is associated with this force is 18 Nm,
what is the angle (1) (we’ll use 9)? (b) What is the sign of thetorque? oTLﬁs (“5 +146, fwalleﬁf’aﬁlz
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0% ’ om Modﬂ Pagac 8—23. A tree grows at an angle of 50° to the ground as shown in Figure 08.5. If the tree is 25 m
from its base to its top, and has a mass of 500 kg, what is the approximate magnitude of the torque on the tree due to the force of gravity? Take the base of the tree as the pivot point.
(The answer is one reason trees need roots.) “The. am7lQ ﬁf’hdﬁen Fauna r” {Ink’f 8—27. Consider the flagpole in Figure P8.27. If the flagpole has a mass of 20 kg and a length of
10 m and the angle the cable makes with the pole is 6 = 25°, what are the magnitude and direction ofthe force exerted by the hinge (at point P) on the flagpole? Assume the mass ofthe
pole is distributed uniformly. . g‘fso (NR—Ha ’H/ic wall ag +(’l€ (oh/0+
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alON W’s 4t 828. The seesaw in Figure P8.28 is 4.5 m long. Its mass of 20 kg is uniformly distributed. The
child on the left end has a mass of 14 kg and is a distance of 1.4 m from the pivot point while a
second child of mass 30 kg stands a distance L from the pivot point, keeping the seesaw at rest.
(a) ls the seesaw in rotational equilibrium? (b) Make a sketch showing all the forces on the
seesaw. Be sure to show where each force acts. (c) Express the conditions for translational and
rotational equilibrium for the seesaw. (d) Solve to find L, the location of the child on the right. I’M ALSumIt/y +L€ Pix/0t T5 at [Zinc aimfer“ o? 'H/LL
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2 9:0 (no x med 2:: .~. +hc ) VlZLQ’A’l/ VA:L r ( 5 838. A flagpole of length 12 m and mass 30 kg is hinged at one end, where it is connected to a
wall as sketched inFigure P838. The pole is held up by a cable attached to the end. Find the ension in he cable.
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 Spring '11
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