1. PHYS 115 EXAM Friday, April 2 10:30-11:20pm Brace 211 first-come first-served with spill-over being seated in Brace 201 Brace 113N Ferg 112 You know the drill by now:

2. Air emerging from the nozzle of a leaf blower is traveling fast, but is only at atmospheric pressure at that point. (A) faster but its pressure was above atmospheric pressure. (B) slower but its pressure was below atmospheric pressure. (C) slower but its pressure was above atmospheric pressure. (D) faster but its pressure was below atmospheric pressure. Before that air reached the nozzle, it was traveling Question 1

3. As streamlines develop around a ball moving gently through the air, the boundary layer ( closest to a ball’s surface ) A. moves the most rapidly. B. moves the most slowly. C. stalls. D. matches the speed of outer layers through its viscosity. E. turbulently mixes with the outer layers that are streaming past. Question 2

4. spin Along the edge turning into the airstream (bottom edge in this picture) A. air speeds up. B. air backs up, slows down. C. airspeed is unaffected. Question 3

5. spin Along the edge turning away with the airstream (top edge in this picture) A. airstreams broaden (lines farther apart). B. airstreams thin (lines closer together). C. airstream spacing remains uniform. Question 4

6. Viewed from directly above, looking down, this pitched ball will A. curve to its right. B. curve to its left left. C. be pushed down (dropping faster than a ball pitched without spin). D. experience an upward lift (dropping faster than a ball pitched without spin). Question 5

7. inside curve outside curve At the bend in a pipe, along the inside curve, the pressure A. decreases. B. can’t change. C. increases. At the bend in a pipe, along the outside curve, the water’s speed A. decreases. B. can’t change. C. increases. Question 6 Question 7

8. The fluid level in the standing open pipes: A. climbs up in pipe 1. B. drops down in pipe 1. C. is unchanged in pipe 1. 1 2 Air is blown across these two manifolds: Question 8

9. A hydrofoil is a ship which can lift its hull up and out of water to reduce its drag. At low speeds, the body of the ship sits in water with its hydrofoils totally submerged. Which of hydrofoil cross sections would work best in providing this lift? As the boat’s speed increases, the hydrofoils create lift. Question 9

10. When hurricane winds blow horizontally past the peaked roof of a house, they tend to lift the roof up, even pulling it off. This upward force develops because the airflow bends down (toward the roof) as it flows over the top. This downward bend indicates the air pressure across the roof’s upper surface is A. equal to atmospheric pressure; a strong, viscous drag pushes the roof up. B. lower than normal atmospheric pressure; an unbalanced pressure pushes the roof up. C. higher than normal atmospheric pressure; an unbalanced pressure pushes the roof up. D. equal to atmospheric pressure; a strong, unbalanced pressure pushes the roof up. Question 10

11. You live in a cylindrical high-rise building with a south-facing window. The air pressure outside the window varies with the wind’s direction. That pressure affects airflow in and out of your window. When the wind blows from east to west, the air pressure outside your window is (A) above atmospheric pressure and air flows out of your window. (B) above atmospheric pressure and air flows into your window. (C) below atmospheric pressure and air flows out of your window. (D) below atmospheric pressure and air flows into your window. Question 11

12. When an airplane lifts its nose too high while flying forward, A. the airstream separates from the bottom surface of its wings and the airplane experiences more lift and less drag. B. the airstream separates from the top surface of its wings and the airplane experiences less lift and more drag. C. the airstream separates from the top surface of its wings and the airplane experiences more lift and less drag. D. the airstream separates from the bottom surface of its wings and the airplane experiences less lift and more drag. Question 11

13. OO ?? Two neutral conductors are connected by a wire and a charged rod is brought near, but does not touch. The wire is taken away, and then the charged rod is removed. What are the sign of the final charges on this pair of conductors? OO +- -+ ++ -- ABCDEABCDE Question 13

14. If the charges are pulled apart to a distance 3d, what is the force on each charge? (a) 9F (b) 3F (c) F (d) 1/3F (e) 1/9F Coulomb’s Law Q F Q F d Q ? Q ? 3d The force between two charges separated a distance d is F. Question 14

15. +2Q+4Q+Q A B C D E Which of the arrows best represents the direction of the net force on charge +Q due to the other two charges? d d Question 15

16. Which of the charges has a greater magnitude? A)B)C) both the same + - + + - + - - What are the signs of the charges whose electric fields are shown above? A) B) C) D) E) no way to tell Question 16 Question 17

17. A 9-volt battery is a source of current that provides A. an electric field accelerating every electron that leaves it with 9 Newtons of force. B. an electric field that accelerating every Coulomb of charge that leaves it with 9 Newtons of force. C. 9 Joules of energy to each electron that leaves it. D. 9 Joules of energy to each Coulomb of charge that leaves it. Question 18

18. Two conducting spheres (radii R 1 and R 2 ) are charged (with Q 1 and Q 2 ), to different potentials V 1 > V 2. This is possible if either A. R 1 > R 2 or Q 1 > Q 2. B. R 1 > R 2 or Q 1 < Q 2. C. R 1 Q 2. D. R 1 < R 2 or Q 1 < Q 2. Question 19

19. If your tires are damp, and the car sits in a puddle of water, is the inside of your car a safe place to stay in a lightning storm? 1. Yes!2. No! Question 20

20. Lecture 30: 20 More Questions! Question: 1.Cslower, but pressure higher (Bernoulli) 2.Bmost slowly (because of viscous drag) 3.Bbacks up, slows down 4.Blines closer together (air is faster here!) 5.Aright (same direction front face is turning!) 6.Adecreases ( viscous drag with surface & crowding of fluid ) 7.Adecreases (wall moves out, opens up more room) 8.Aclimbs. Airstream curving down means low pressure! 9.CLift must have fast, low pressure air across top. 10.BAirstream curving down means low pressure. 11.CLow pressure; air flows out. 12.BAirstream sheers from top; lift is lost. 13.B+ driven away from rod, - charge drawn toward it. 14.E1/9 th (inverse square law!0 15.Bforce up twice that of force to the right 16.DE-fields point away from +, toward - charges. 17.Bmore field lines = stronger E-field 18.D9 Joules/Coulomb 19.CEither more charge, or more tightly packed. 20.AYes. The metal frame and body is a conductor.