Physics 1050 - Fall 2014 - Midterm Exam 2 - Posted Version
Problem 1:
A block of wood floats motionless on a calm lake. Part of the block is in water and part of it is in air. As the day becomes hotter and the density of the air decreases, the block of wood
(A) becomes heavier, but it continues to float exactly as it did before the air became hotter.
(B) becomes lighter, but it continues to float exactly as it did before the air became hotter.
(C) moves downward so that more of the block is in water and less of the block is in air.
(D) moves upward so that more of the block is in air and less of the block is in water.
Problem 2:
A gymnasium has a large ventilation duct near its ceiling. When air that was moving at uniform velocity and pressure through a straight section of that duct enters a bend in the duct, its pressure is greatest at the [neglect any effects due to viscosity, turbulence, or gravity]
(A) outside of the bend and its speed is greatest at the outside of the bend.
(B) outside of the bend and its speed is greatest at the inside of the bend.
(C) inside of the bend and its speed is greatest at the outside of the bend.
(D) inside of the bend and its speed is greatest at the inside of the bend.
Problem 3:
Firefighters are battling a fire on the 8th floor of an apartment building. When they stand on the ground, their fire hose can only shoot the water steadily up to the 6th floor. So they carry the nozzle end of the same fire hose to the top of a 2-story-tall ladder and again direct its spray upward. Now the fire hose can shoot the water steadily up to the [neglect any effects due to viscosity or turbulence]
(A) 8th floor.
(B) 4th floor.
(C) 6th floor.
(D) 7th floor.
Problem 4:
You accidently drop a coin on a smooth floor and the coin rolls on its thin edge for an astonishingly long distance. You can see the coin tipping to one side or the other occasionally, but it always returns to upright and continues rolling all the way across the room. Why did the coin manage to roll so far without falling flat on the floor?
(A) The coin has static stability that prevents it from falling over.
(B) Each time the coin started tipping over, it steered itself automatically to put its contact point with the ground under its center of gravity.
(C) Each time the coin started tipping over, it forward velocity increases and its greater apparent weight causes it to return to upright.
(D) The coin is pushed upward by the buoyant force and floats back to upright after it begins to tip.
Problem 5:
You are riding a rollercoaster with a loop-the-loop. You have just rolled up the side of the loop and are, at this moment, exactly at the top of the loop. You and the car are upside down, yet you are pressed tightly into your seat. At this moment, you are accelerating
(A) upward at a rate equal in amount to the acceleration due to gravity.
(B) downward at less than the acceleration due to gravity.
(C) downward at more than the acceleration due to gravity.
(D) downward at the acceleration due to gravity.
Problem 6:
You are jogging northward along the ocean on a calm, windless day and are experiencing a pressure drag force that pushes you southward. A viewed by someone standing motionless on the beach, the average velocity of the air a few inches (a few centimeters) behind you is
(A) zero and that air is calm and motionless.
(B) greater than zero and directed northward.
(C) greater than zero and directed southward.
(D) zero, but that air is swirling rapidly in all directions.
Problem 7:
You are competing in the 400-meter sprint on an oval track. As you round the final turn at world record pace, your path is curving toward your left and you find yourself leaning toward the left. Why can't you complete the turn safely if you don't lean and instead try to remain upright during the turn?
(A) Your feet will accelerate toward your left while your body coasts straight forward and you will tip over.
(B) Your center of gravity will not be above your base of support on the track and you will not have static stability.
(C) Your center of gravity will be too high above the ground and you will have too much energy to complete the turn safely.
(D) The track's force on your feet will make you accelerate toward your center of mass and tip over.
Problem 8:
You are drying your hair and you have put a diffuser (an anti-nozzle) on the end of the dryer. As it goes through the diffuser, the air slows down and its
(A) pressure increases.
(B) density decreases.
(C) particle density decreases.
(D) momentum increases.
Problem 9:
You are a firefighter and the alarm sounds in your fire station. You are on the second floor, so you grab hold of the metal fire pole and slide down it to the first floor. As you are sliding down the fire pole at constant velocity, your gravitational potential energy is decreasing. What is becoming of that energy?
(A) It is becoming thermal energy.
(B) It is becoming kinetic energy.
(C) It is becoming downward force.
(D) It is becoming downward momentum.
Problem 10:
The water tower in your town's water distribution system stores water and ensures that there is a steady water pressure in all of the pipes, regardless of how much water is being used at any time. The town council asks you to increase the water pressure in the pipes, so you make the water tower [neglect effects due to viscosity or turbulence]
(A) wider (increase its diameter).
(B) shorter (decrease its altitude).
(C) narrower (decrease its diameter).
(D) taller (increase its altitude).
Problem 11:
You are in a bicycle race on a hilly course and you go over a big bump so fast that your bicycle loses contact with the ground. While the bicycle is not touching the ground, you are
(A) not accelerating, but you feel heavier than you do at rest.
(B) not accelerating, but you feel lighter than you do while at rest.
(C) accelerating downward and you feel heavier than you do at rest.
(D) accelerating downward and you feel lighter than you do while at rest.
Problem 12:
You are cleaning your car with water from a hose and nozzle. At the center of the stream of water, right where it hits the side of your car, the water is almost coming to a complete stop and its water pressure is
(A) equal to atmospheric pressure.
(B) exactly zero.
(C) lower than atmospheric pressure, but more than zero.
(D) higher than atmospheric pressure.
Problem 13:
A tennis player hits the tennis ball forward with "topspin," meaning that the top of the ball is moving forward relative to the rest of the ball. This spinning ball experiences a strong downward lift force and bends downward toward the ground after going over the net. One reason why this ball is experiencing that aerodynamic lift force is that the ball's spin
(A) exerts a torque on the ball that causes its angular momentum to shift downward.
(B) exerts a torque on the ball that causes its angular momentum to shift upward.
(C) causes the air to flow faster and farther around the bottom of the ball than around the top of the ball.
(D) causes the air to flow faster and farther around the top of the ball than around the bottom of the ball.
Problem 14:
When air is flowing past a ball, the most difficult part of its passage is from the middle of the ball to the back of the ball. During that part of the air's journey, the air pressure along each streamline
(A) increases and the airflow slows down.
(B) decreases and the airflow speeds up.
(C) increases and the airflow speeds up.
(D) decreases and the airflow slows down.
Problem 15:
Your plastic bottle of ketchup is almost empty, so you cap the bottle and swing it rapidly in a circle with the cap end pointing outward. The remaining ketchup accumulates just inside the cap and you can squirt it on your fries. This technique works because
(A) the force of the ketchup's momentum pushes it toward the cap end of the bottle.
(B) viscous forces push the ketchup toward the cap end of the bottle.
(C) the bottle's rapid acceleration toward the center of the circle leaves the ketchup's behind so that it drifts toward the cap end of the bottle.
(D) centrifugal force pushes the ketchup toward the cap end of the bottle.
Problem 16:
On a hot afternoon, you seal your empty plastic water bottle and thus trap the hot air inside it. Later in the day, the bottle and its contents are much cooler and the elastic sides of the bottle are now bent inward. The bottle's volume has decreased. Based on these changes, you can be certain that the air pressure inside the bottle has
(A) decreased, but the density inside the bottle has decreased.
(B) decreased and the density inside the bottle has increased.
(C) decreased, but the density inside the bottle has stayed the same.
(D) stayed the same, but the density inside the bottle has increased.
Problem 17:
As water flows downward in a vertical pipe that has a uniform diameter, the water's gravitational potential energy decreases,
(A) its kinetic energy increases, but its pressure potential energy remains constant.
(B) and both its pressure potential energy and its kinetic energy increase.
(C) its pressure potential energy increases, but its kinetic energy remains constant.
(D) but neither its pressure potential energy nor its kinetic energy change.
Problem 18:
As a rocket takes off from its launch pad, a plume of flaming exhaust gas squirts out of its engine and scorches the launch pad. What is exerting the upward force on the rocket that causes the rocket to accelerate upward?
(A) The air is pushing the rocket upward.
(B) The exhaust gas is pushing the rocket upward.
(C) The launch pad is pushing the rocket upward.
(D) The entire Earth is pushing the rocket upward.
Problem 19:
A rocket designed to put a satellite in orbit around the earth has two main tasks. First, it must lift the satellite above earth's atmosphere to eliminate air resistance. Second, it must
(A) push upward on the satellite with a force that balances the satellite's downward weight so that the satellite can coast at constant velocity.
(B) give the satellite such a large sideways acceleration that the satellite's apparent weight is zero.
(C) give the satellite such a large horizontal speed that the falling satellite arcs endlessly around the earth rather than descending to the ground.
(D) give the satellite such a large upward vertical speed that the falling satellite cannot descend to the ground.
Problem 20:
You are standing in a slow-moving stream, facing upstream so that the water is coming toward the front of your body. You are wearing shorts and the water level is slightly above your bare knees. The water experiences perfect laminar flow around each of your nearly cylindrical legs. You measure the water pressure at a specific altitude below your right knee and find that the water pressure is
(A) largest on the front and back of your leg and smallest on the sides of your leg.
(B) smallest on the front of your leg, largest on the sides of your leg, and medium on the back of your leg.
(C) the same all the way around your leg, since you are measuring the pressure at constant altitude.
(D) largest on the front of your leg, medium on the sides of your leg, and smallest on the back of your leg.
Problem 21:
You kick a soccer ball so that it curves toward your left as it travels toward the goal. The ball curves toward your left because
(A) it is deflecting the airflow around it toward your left.
(B) the pressure in front of it is higher than the pressure behind it.
(C) it is deflecting the airflow around it toward your right.
(D) you exerted a leftward force on it with your foot.
Problem 22:
You are pulling a wagon full of children up a hill at constant velocity. Which one of the following statements is true?
(A) The net force on the wagon is uphill and you are doing zero work on the wagon.
(B) The net force on the wagon is zero and you are doing work on the wagon.
(C) The net force on the wagon is zero and you are doing zero work on the wagon.
(D) The net force on the wagon is uphill and you are doing work on the wagon.
Problem 23:
You drop an unopened metal can of soup and it lands bottom-first on the floor. When you inspect the can, you see that part of it has dented outward. Where did it dent outward and why?
(A) The pressure near the bottom of the can increased dramatically as the soup transferred its momentum suddenly to the floor and that pressure dented the can outward near its bottom.
(B) The impact between the floor and the bottom of the can buckled the can outward near its middle (halfway between its top and bottom).
(C) The soup bounced upward after the can hit the floor and when the soup hit the top of the can, it dented the top of the can outward.
(D) The floor pushed the bottom of the can upward extremely hard on impact and the momentum of that upward force dented the can outward near its top.
Problem 24:
As you accelerate forward at the start of a marathon (a long-distance running race), what force or forces is the level ground exerting on you?
(A) A horizontal frictional force that is directed forward.
(B) An upward support force and a horizontal frictional force that is directed forward.
(C) An upward support force.
(D) A horizontal support force that is directed forward.
Problem 25:
You are trying to set the world's record for drinking water through the tallest drinking straw. What could you do to have the best chance of setting this record?
(A) Use the narrowest drinking straw you can find.
(B) Use the widest drinking straw you can fit in your mouth.
(C) Choose a bad-weather day when the atmospheric pressure is as small as possible.
(D) Choose a good-weather day when the atmospheric pressure is as large as possible.
Problem 26:
Two shiny plastic balloons are identical in every way except that one contains air and the other contains helium. The balloons have
(A) different weights, particle densities, and densities.
(B) the same densities, but they have different particle densities and different total weights.
(C) the same weights, but they have different particle densities and different densities.
(D) the same particle densities, but they have different densities and different total weights.
Problem 27:
You are standing on the level metal platform of a carousel, talking to a child who is riding a nearby horse. As the carousel turns, you travel in a circle. Suddenly oil leaks from the engine operating the carousel and the platform you are standing on becomes perfectly slippery: no friction! Since the only thing you are touching is the rotating horizontal platform,
(A) you continue to travel in a circle at constant velocity.
(B) your motion becomes centripetal and you head toward the center of the carousel.
(C) you move at constant velocity with the velocity you had just before the oil leak.
(D) your motion becomes centrifugal and you head directly away from the center of the carousel.
Problem 28:
A building with two floors has simple plumbing with no moving parts. If you try the showers on each floor, you will find that [neglect any effects due to viscosity or turbulence]
(A) the ordered energy per drop is the same on both floors and that both floors have the same pressure before the shower head and produce equally fast moving water after the shower head.
(B) the upper floor has less ordered energy per drop, less pressure before the shower head, and slower moving water after the shower head.
(C) the ordered energy per drop and the pressure before the shower head are the same on both floors, however, the upper floor has slower moving water after the shower head.
(D) the ordered energy per drop is the same on both floors, however, the upper floor has less pressure before the shower head and slower moving water after the shower head.
Problem 29:
Water is flowing gently out of the end of a garden hose. You block off most of the hose's opening with your thumb and now the water sprays out at high speed because you
(A) are compressing the water and increasing its density.
(B) are keeping air from getting into the hose and reducing the water pressure.
(C) have reduced the water's speed in the hose so that it wastes less of its ordered energy.
(D) are doing work on the water with your thumb and greatly increasing its ordered energy.
Problem 30:
In racquetball, players take turns hitting a rubber ball forward so that it bounces off the front wall of a box-like court. The ball is very lively, so it bounces backward at almost the same speed it had before the bounce. During its bounce, the ball retains approximately all of its
(A) energy and momentum.
(B) energy but transfers most of its momentum to the front wall.
(C) energy but transfers more forward momentum than it had to the front wall.
(D) momentum but transfers most of its energy to the front wall.