Group_________ Physics 140 Discussion #7 Student Name (Last, First): 1.2.3. 4.5. Q5.29. A ball is dropped from rest and feels air resistance as it falls. Which of the graphs in Fig. 5.39 best represents its accelera tion as a function of time? (a) (b) (c) (d) (e) a a Q5.30. A ball is dropped from rest and feels air resistance as it falls. Which of the graphs in Fig. 5.40 best represents its vertical velocity component as a function of time? (a) (b) (c) (d) (e) 0 o H 5.42. A 25.0-kg box of textbooks rests on a loading ramp that makes an angle a with the horizontal. The coefficient of kinetic friction is 0.25, and the coefficient of static friction is 0.35. (a) As the angle a is increased, find the minimum angle at which the box starts to slip. (b) At this angle, find the acceleration once the box has begun to move. (c) At this angle, how fast will the box be mov ing after it has slid 5.0 m along the loading ramp? 5.95. Banked Curve I. A curve with a 120-rn radius on a level road is banked at the correct angle for a speed of 20 rn/s. If an automobile rounds this curve at 30 m/s, what is the minimum coefficient of static friction needed between tires and road to pre vent skidding? 0 0 5.52. The ?Giant Swing? at a county lair consists of a vertical cen tral shaft with a number oF horizontal arms attached at its upper end (Fig. 5.57). Each arm supports a seat suspended from a cable 5.00 rn long, the upper end of the cable being fastened to the arm at a point 3.00 m from the central shaft. (a) Find the time of one rev olution of the swing if the cable supporting a seat makes an angle of 30.00 with the vertical. (b) Does the angle depend on the weight of the passenger for a given rate of revolution? 5.106. A small rock moves in water, and the force exerted on it by the water is given by Eq. (5.7). The terminal speed of the rock is measured and found to be 2.0 mIs. The rock is projected upward at an initial speed of 6.0 in/s. You can ignore the buoyancy force on the rock. (a) In the absence of fluid resistance, how high will the rock rise and how long will it take to reach this maximum height? (b) When the effects of fluid resistance are included, what are the answers to the questions in part (a)? Figure 5.57 Exercise 5.52. 5.119. A small block with mass m is placed inside an inverted I cone that is rotating about a ver- I \\ tical axis such that the time for Figure 5.83 Problem 5.119. one revolution of the cone is T (Fig. 5.83). The walls of the cone make an ang1e with the - - vertical. The coefficient of static - friction between the block and the cone is p1. If the block is to I remain at a constant height h above the apex of the cone, what fl 17 are the maximum and minimum / values of T? 3 P ?is ci c1 ?I 0 11 11 P -if Cl.. ?4 ii ?0 1? I a t U fl ,2 ?% ) IcC , U l 9- 0 c ?3 3- 4 9- I I Ii, H b N I) Cd) CI) cj\ II C >c r ii 4 ii b (Th . %J) \I1 . K, zI -t 1? (1 (A > ?-?F \tj/ Cl) __ ci cc cJ U ?U C oc) C, Cp j J cy\ 4 N f)i fl 0 cs c) \iJ (s C?.? $ V ci 0 c)J Li 1 1) V I -.c ?I 3, 3 ?1 zc ÷ \% a 1(4 F If > II LI I (4 \i/ C 1 1 %1J -p 4. Ii -4- C-. ,?1 o (4% L( 4 Lc ?I I.? 11 ?1? ) 1) 1 C5% it 91 1 .4- 4- Ii -4- ii 4 4- ?C 1 A zē k I + -kc u U It it 1- (2 r cD 11. It c?r if > -z ?I 1? I? i I I. 11 I -c ii? (.?II-I. >\ I 1 -t I jLZ -1t ii __ t 1\ I - -z I c) ?1 e11 f??) ?? I I r/ *7 1 II
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