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PHYS 115 EXAM Wednesay, October 24 10:30-11:20pm Brace 211 Brace 113 Brace 201 Brace 305 You draw back a rubber band 20 cm (8 inches) and feel the 10 N force it pulls back with. A. 0 Newtons. B. 10 Newtons. C. 20 Newtons. D. 30 Newtons. E. 40 Newtons. Force Hoping to shoot it all the way across the room you pull it back a full 60 cm (24 in). How great is the force needed to hold it there (steady at rest)? Distance Hoping to shoot it all the way across the room you pull it back a full 60 cm. It takes 30 N of force to hold it there. How much work did you do in stretching it? A. 0 Joules B. (15 N)(0.60 m) = 9 Joules. C. (30 N)(0.60 m) = 18 Joules. D. (45 N)(0.60 m) = 27 Joules. E. (60 N)(0.60 m) = 36 Joules. Hoping to shoot it all the way across the room you pull it back a full 60 cm. It takes 30 N of force to hold it there. What average force did you exert in pulling it back this far? 30 N Force A. 30 Newtons. B. 20 Newtons. C. 15 Newtons. D. 10 Newtons. E. 5 Newtons. Distance Hoping to shoot it all the way across the room you pull it back a full 60 cm. It takes 30 N of force to hold it there. How much work did you do in stretching it? A. 0 Joules B. (15 N)(0.60 m) = 9 Joules. C. (30 N)(0.60 m) = 18 Joules. D. (45 N)(0.60 m) = 27 Joules. E. (60 N)(0.60 m) = 36 Joules. Hoping to shoot it all the way across the room you pull it back a full 60 cm. It takes 30 N of force to hold it there. You performed 9 Joules of work in stretching it. When released, the rubber band flies off with what kinetic energy? A. 0 Joules B. 3 Joules. C. 4.5 Joules. D. 9 Joules. E. You need to know the band’s mass. A rider in the “barrel of fun” at the State Fair midway has her back “pinned” to the wall. Which diagram correctly shows the forces acting in her? A. D. B. E. C. F. In the game of tetherball, the struck ball whirls around a pole. In what direction does the net force on the ball point? E A C A. Towards the top of the pole B. Down, towards the ground C. Horizontal, in toward the pole. D. Horizontal, out from the pole. E. Up along the vertical component of the tension force E. Tangential to the circle D F B You do NOT slow down to take the left curve in the road ahead, or speed up at any point in it, but instead enter and leave the turn at exactly the same speed. During this left turn your car is A. moving with constant velocity. B. accelerating backward. C. accelerating left. D. accelerating right. A fighter pilot making a sharp turn will pass out if the acceleration he experiences is more than 9g’s (9 the acceleration of gravity). If his F18 is moving with a speed of 300 m/s, what is the approximate radius of the tightest turn this pilot can survive ? A) 500 m B) 1000 m C) 2000 m The angular momentum of this merry-go-round points A. right. B. left. C. up. D. down. E. into the screen. F. out of the screen. G. clockwise H. counter-clockwise. This hand-cranked flashlight is pointed (mostly) out of the screen toward you. The torque being applied to power it up is in what direction? A.clockwise B. counterclockwise C. forward (out of the screen) D. left E. right Torques and the angular momentum (spin) they produce are assigned directions by the “Right Hand Rule.” This wheel is rolling away from you (into the screen): Its angular momentum points in what direction? A. right. B. left. C. down. D. up. E. into the screen. F. out of the screen. The mass of Mars is 1/10 that of Earth, and its radius is 1/2 that of Earth. What is the acceleration of gravity on Mars? (A) (B) (C) (D) (E) 0.1 g 0.2 g 0.4 g 0.5 g 0.8 g The 90-kg fullback runs up the middle at 8 m/sec straight into the waiting arms of the 110-kg defensive tackle. The tackle wraps his arms about the fullback and the two are carried along together by the fullback’s momentum with what speed? A. B. C. D. 3.6 m/sec 5.4 m/sec 6.5 m/sec 7.2 m/sec When stopped at the top of a Ferris wheel, the normal force exerted by your seat is equal to your weight. How does the normal force supporting you change as you glide rapidly past the top? A) The normal force stays the same. B) The normal force becomes smaller. C) The normal force becomes larger. You are at an amusement park, taking a ride on the Super Shot drop tower. After lifting you hundreds of feet in the air, this ride simply drops you. As you plummet, (A) your constant momentum downward gives you feeling a of weightless. (B) though moving down you experience a sense of velocity up. (C) you are accelerating down at the same rate as all your organs giving a sensation of weightlessness. (D) you are moving down at constant velocity and therefore feel weightless. Two different balloons are inflated with air: a rubber balloon and a Mylar balloon. The rubber expands as its pressure increases, but the Mylar one cannot increase in volume. If both are left out in the hot sun, the upward buoyant force on the rubber balloon will (A) increase, but decrease for the Mylar balloon. (B) remain the same, but decrease for the Mylar. (C) increase, while it doesn’t change at all for the Mylar balloon. (D) increase, and also increase for the Mylar balloon as well. (E) decrease, while increasing for the Mylar. (F) decrease, and also decrease for the Mylar. Bullets strike Superman in the chest and stomach! An initial volley catches him unprepared, but not the second!!!! Some bounce right back, while others were stopped dead, dropping to the earth. Which delivered the greater force of impact? A. the bounced bullets B. the stopped bullets C. both the same. The center of gravity of each of the trucks is shown by the black dot. Which of the trucks will tip over? 1) 2) 3) 4) 5) 6) A B C A and C all of them none of them A box is placed on a ramp in the configurations shown below. Friction prevents it from sliding. The center of mass of the box is indicated by a blue dot in each case. In which cases does the box tip over ? 1 (a) all 3 2 (b) 2 & 3 (c) 3 only Lecture 21: 20 Questions Question: 1. D 30 Newtons 2. B 9 Joules. 3. C 15 Newtons 4. B 9 Joules 5. D 9 Joules 6. F Circular motion centr. F 7. C toward the pole 8. C accelerating to the left. 9. B a=v2/R R= v2/a (a=9g) R=1020m. 10. C up 11. E right (use the thumb of your curled right hand) 12. B left 13. C 4/10 14. A 90(8)+0=(200)v v=720/200 15. B smaller. 16. C accelerating down 17. C increases for rubber, no change for Mylar 18. A Bounced bullets=twice the impulse of stopped. 19. A Center of mass not over base. 20. C 3 only.