exam 3 PHYS 122 Fall 2007 solutions

# exam 3 PHYS 122 Fall 2007 solutions - 1 A spring-loaded toy...

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Unformatted text preview: 1. A spring-loaded toy gun is used to shoot a ball straight up in the air. The ball reaches a maximum height H, measured from the equilibrium position of the spring. The same ball is shot straight up a second time from the same gun, but this time the spring is compressed only half as far before ﬁring. How far up does the ball go this time? Neglect friction. Assume that the spring is ideal and that the l a 2 “g ' L 2 firth ' . J- r v ' ~1.; ' ' “ %\\X2 3 “MTV \ /I d. H/32 L .f i/ 'Z5~;iw"l\2 % ﬁlm“ 1 2. You carry a 7.0 kg bag of groceries 1.2 m above the ground at a constant velocity acmW room. How much word do you do on the bag in the process? 093” / *~ 1: \ b' 82 J \'\l '1‘? W} (:03 6; I” H C c. 151 J I K d' 128 J W 5 U 3. An astronaut is in equilibrium when he is positioned 400 km from planet X and 600 km from planet Y, along a straight line joining the planets centers. What is the ratio of the masses X/Y? c. 15 ) ‘/ d. 2.3 a .- I , q .2” w“ ’7‘" Z, l”) T '2 DU) 2. {1 [WA ~ ~ ” :’ (1,: W ’" (12913-- " we»? 7 4. An earth satellite needs to have its orbit) changed so the new orbit will be twice as far from the center of the earth as the original orbit. The new orbital period will be twice as long as the original period. ‘ ,2}.._Irue¢\ 7 b. False”:e T» 394 a. What is the ﬁnal kinetic energy of thee 'mney j \ ground? Your answer should be left in terms of m and (MK 06' L,“ K? L59: 7 ﬂ/ {n.rz.z\\«5\ : -- » V '2? i“: "I: L: E ( Ll '7 “- :r- "La- ! krth ) a” b. What is the initial potential energy of the chimney? Your answer should be left in terms of m and L. (“V ’3 m C73") \ \ f\ f» /‘. ~- _ . _ :90 L81 "HE C("CLL {WC c. When the tip of the chimney 15 Q m W‘s, what IS the chimney’s angular speed 03f? 2 L? (\ QWGB; ( 2‘ SC", /C, ‘3‘ ‘ N‘ g - r “(UH LIA I} ( \ g” he), 4 (“'3”) l’ L ( pl“; C757"? (-2 ( ‘ 7”" J 4 " LL : M t “7‘ V / ‘ . \ ,-_. .1,“ I f t 3' t a“? L~ l (44: (g; m) (a 7 ’v _\.\ M / . 2 WW? ,, 291.9. .. 2, it ;;é:ie.:../f “‘ 1 Le I 6. A 100 N cannon ball is ﬁred at a speed of 20 m/s off a 25 m tall fortress wall at an angle of 30° above the horizontal. a. Find the speed of the cannon ball right before it strikes the ground (assume the ground is level). .7 ‘ evil; <' 1' "0c '\ \fe CLJL‘v cm GA 1’4: 7&1" r, .2 er C b. If instead the cannon ball were ﬁred at 20 m/s 600 below the horizontal, what would the speed of the cannon ball be right before impact? ., __ __ up; + w * Ma lki \ I :L -.,') 1‘— ‘,v’t'xi~\\\ *‘ é” .37“ V ‘ Z l V” a 7. A force I?“ =125—10} N acts on an object. a. How much work does this force do as the object moves from the origin to the point 7 =14i+11j m? b. The same force is applied to a point F = 8} which gives rise to a torque about the origin. Find the W torque. 8. A particular motor can provide a maximum of 1 10.0 Nm of torque. Assuming that all of this torque issued to accelerate a solid ﬂywheel (Imjt‘mrz) of mass 10.0 kg and radius 4.00 m. Z a. What is the angular acceleration of the ﬂywheel? : a; my?» «4 in; M 07 : “It: ’5‘”) (CW) M {X ‘: (TACK/3 2—“ T3 b. How long will it take for the ﬂywheel to accelerate ﬁ-Om rest to 11.00 rad/S? ‘ I“ n l a ,,/L‘.(.‘! I] vﬂC/Sa ,,. ‘25 .P‘ r IJ h M; c. What is magnitude of the ﬂywheel’s‘ahgular momentum? // ,1 > 1’» C V Y _ 9% l» 5““ V6 ...
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