PHYS 115 EXAM Friday, April 2 10:30-11:20pm

Brace 211first-come first-served

with spill-over being seated in

Brace 201Brace 113N

Ferg 112

You know the drill by now:

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 thenozzle, it was traveling

Question 1

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

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

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

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

insidecurve

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

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.

12

Air is blown across these two manifolds:

Question 8

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 wouldwork best in providing this lift?

As the boat’s speed increases,the hydrofoils create lift.

Question 9

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

You live in a cylindrical high-rise building with a south-facing window. Theair pressure outside the window varies with the wind’s direction. That pressure affects airflow inand 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

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

O O

? ?

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?

O O

+ -

- +

+ +

- -

A

B

C

D

E

Question 13

If the charges are pulled apart to a distance 3d, what is the force on each charge?

(a)(a) 9F9F (b) (b) 3F3F (c) (c) FF (d) (d) 1/3F1/3F (e) (e) 1/9F1/9F

Coulomb’s Law Q

FQ

F

d

Q?

Q?

3d

The force between two charges separated a distance d is F.

Question 14

+2Q

+4Q

+Q

A BC

DE

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

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

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

Two conducting spheres (radii R1 and R2)

are charged (with Q1 and Q2),

to different potentials V1 > V2.

This is possible if either

A. R1 > R2 or Q1 > Q2.B. R1 > R2 or Q1 < Q2.C. R1 < R2 or Q1 > Q2.D. R1 < R2 or Q1 < Q2.

Question 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

Lecture 30: 20 More Questions!Question: 1. C slower, but pressure higher (Bernoulli) 2. B most slowly (because of viscous drag) 3. B backs up, slows down 4. B lines closer together (air is faster here!) 5. A right (same direction front face is turning!) 6. A decreases (viscous drag with surface & crowding of fluid) 7. A decreases (wall moves out, opens up more room) 8. A climbs. Airstream curving down means low pressure! 9. C Lift must have fast, low pressure air across top.10. B Airstream curving down means low pressure.11. C Low pressure; air flows out.12. B Airstream sheers from top; lift is lost.13. B + driven away from rod, - charge drawn toward it.14. E 1/9th (inverse square law!015. B force up twice that of force to the right16. D E-fields point away from +, toward - charges.17. B more field lines = stronger E-field18. D 9 Joules/Coulomb19. C Either more charge, or more tightly packed. 20. A Yes. The metal frame and body is a conductor.