Physics 2 ch 15

Two horizontal pipes have the same diameter, but pipe B is twice as long as pipe A. Water undergoes viscous flow in both pipes, subject to the same pressure difference across the lengths of the pipes. If the flow rate in pipe B is Q = change in V/ change in time (t) what is the flow rate in pipe A? A) 2Q B) Q square root 2 C) 8Q D) 16Q E) 4Q

A) 2 Q

A closed cubical chamber resting on the floor contains oil and a piston. If you push down on the piston hard enough to increase the pressure just below the piston by an amount change in p, which of the following statements is correct? (There could be more than one correct choice.) A) The increase in the force on the top of the chamber will be the same as the increase in the force on the bottom of the chamber. B) The pressure everywhere in the oil will increase by change in p. C) The pressure on the sides of the chamber will not increase. D) The pressure at the bottom of the oil will increase by more than change in p. E) The pressure at the top of the oil will increase by less than change in p.

A) The increase in the force on the top of the chamber will be the same as the increase in the force on the bottom of the chamber. B) The pressure everywhere in the oil will increase by change in p.

A steel ball sinks in water but floats in a pool of mercury, which is much denser than water. Where is the buoyant force on the ball greater? A) floating on the mercury B) It is the same in both cases. C) submerged in the water D) It cannot be determined from the information given.

A) floating on the mercury

A piece of iron rests on top of a piece of wood floating in a bathtub. If the iron is removed from the wood, and kept out of the water, what happens to the water level in the tub? A) It goes down. B) It does not change. C) It goes up. D) It is impossible to determine from the information given.

A) it goes down

Salt water is denser than fresh water. A ship floats in both fresh water and salt water. Compared to the fresh water, the volume of water displaced in the salt water is A) less. B) more. C) the same. D) Cannot be determined because we do not know the volume of the ship.

A) less

A hollow sphere of negligible mass and radius R is completely filled with a liquid so that its density is p. You now enlarge the sphere so its radius is 2R and completely fill it with the same liquid. What is the density of the enlarged sphere? A) p B) p/2 C) p/8 D) 4p E) 8p

A) p

A 50-cm3 block of wood is floating on water, and a 50-cm3 chunk of iron is totally submerged in the water. Which one has the greater buoyant force on it? A) the iron B) Both have the same buoyant force. C) the wood D) It cannot be determined without knowing their densities.

A) the iron

Substance A has a density of 3 g/cm3 and substance B has a density of 4 g/cm3. In order to obtain equal masses of these two substances, what must be the ratio of the volume of A to the volume of B? A) square root 3/4 B) 4/3 C) 3/1 D) 3/4 E) 1/3

B) 4/3

When a heavy metal block is supported by a cylindrical vertical post of radius R, it exerts a force F on the post. If the diameter of the post is increased to 2R, what force does the block now exert on the post? A) F/2 B) F C) 2F D) F/ square root 2 E) F/4

B) F

Water flows through a pipe. The diameter of the pipe at point B is larger than at point A. Where is the water pressure greatest? A) at point A B) at point B C) It is the same at both A and B.

B) at point B

A wooden block contains some nails so that its density is exactly equal to that of water. If it is placed in a tank of water and released from rest when it is completely submerged, it will A) sink to the bottom. B) remain where it is released. C) rise to the surface.

B) remain where it is released.

A 10-kg piece of aluminum sits at the bottom of a lake, right next to a 10-kg piece of lead, which is much denser than aluminum. Which one has the greater buoyant force on it? A) Both have the same buoyant force. B) the aluminum C) the lead D) It cannot be determined without knowing their volumes.

B) the aluminum

Two horizontal pipes are the same length, but pipe B has twice the diameter of pipe A. Water undergoes viscous flow in both pipes, subject to the same pressure difference across the lengths of the pipes. If the flow rate in pipe A is Q = change in V/ change in time (t) , what is the flow rate in pipe B? A) 8Q B) 4Q C) 16Q D) 2Q E) Q square root 2

C) 16 Q

A piece of wood is floating in a bathtub. A second piece of wood sits on top of the first piece, and does not touch the water. If the top piece is taken off and placed in the water, what happens to the water level in the tub? A) It goes down. B) It goes up. C) It does not change. D) It cannot be determined without knowing the volumes of the two pieces of wood.

C) It does not change.

The water pressure to an apartment is increased by the water company. The water enters the apartment through an entrance valve at the front of the apartment. Where will the increase in the static water pressure be greatest when no water is flowing in the system? A) at a faucet close to the entrance valve B) at a faucet far from the entrance valve C) It will be the same at all faucets. D) There will be no increase in the pressure at the faucets.

C) It will be the same at all faucets.

Salt water has greater density than fresh water. A boat floats in both fresh water and in salt water. Where is the buoyant force greater on the boat? A) in fresh water B) in salt water C) The buoyant force is the same in both cases.

C) The buoyant force is the same in both cases.

A boat loaded with rocks is floating in a swimming pool. If the rocks are thrown into the pool, the water level in the pool, after the rocks have settled to the bottom, A) stays the same. B) rises. C) falls

C) falls

When a box rests on a round sheet of wood on the ground, it exerts an average pressure p on the wood. If the wood is replaced by a sheet that has half the diameter of the original piece, what is the new average pressure? A) p square root 2 B) p/4 C) 2p D) 4p E) p/2

D) 4p

As a rock sinks deeper and deeper into water of constant density, what happens to the buoyant force on it if it started above the surface of the water? A) The buoyant force steadily decreases. B) The buoyant force keeps increasing steadily. C) The buoyant force remains constant. D) The buoyant force first increases and then remains constant.

D) The buoyant force first increases and then remains constant.

Consider a brick that is totally immersed in water, with the long edge of the brick vertical. The pressure on the brick is A) greatest on the face with largest area. B) greatest on the top of the brick. C) the same on all surfaces of the brick. D) greatest on the bottom of the brick. E) greatest on the sides of the brick.

D) greatest on the bottom of the brick.

An air bubble underwater has the same pressure as that of the surrounding water. As the air bubble rises toward the surface (and its temperature remains constant), the volume of the air bubble A) decreases. B) remains constant. C) increases or decreases, depending on the rate it rises. D) increases.

D) increases

A styrofoam sphere of radius R has a density p. You now carefully compress the sphere so its radius is R/2. What is the density of the compressed sphere? A) 4p B) 2p C) p square root 8 D) p square root 2 E) 8 p

E) 8p