Problem 1:
Suppose a huge alien spaceship were to visit us and remove half the molecules from the earth's atmosphere. The air pressure at sea level would then be approximately
Answer: (C) 50% of its original value. [66.8% picked]
Why: Video Discussion
Problem 2:
When water flows around a bend in a garden hose, the water pressure
Answer: (B) decreases near the inside of the curve and increases near the outside of the curve. [75.2% picked]
Why: Video Discussion
Problem 3:
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?
Answer: (B) Go to the lowest altitude available, preferably sea level or below. [38.1% picked]
Why: Video Discussion
Problem 4:
When you pour milk from a pitcher into a bowl, the flow is likely to become turbulent. When you pour honey from a jar into a bowl, however, the flow is likely to remain laminar. Compared to milk, honey is more likely to exhibit laminar flow because honey's larger
Answer: (B) viscosity tends to keep the flow orderly. [94.2% picked]
Why: Video Discussion
Problem 5:
You are holding an umbrella over your head on a windy day. As the wind blows across the dome-shaped top of the umbrella, the airstream is curving toward the umbrella's surface. The air pressure just above the peak of the umbrella is
Answer: (A) less than atmospheric pressure. [70.4% picked]
Why: Video Discussion
Problem 6:
You are standing 10 feet north of a campfire in a level, open field. Despite the cool air all around you, you feel warmed by the fire. Heat is flowing from the fire to you
Answer: (A) mostly via thermal radiation. [73.9% picked]
Why: Video Discussion
Problem 7:
You are drying your hair and you have put a diffuser (an anti-nozzle) on the end of the dryer, so that it doesn't blow your naturally curly hair straight. As fast-moving air from the dryer flows through the diffuser, that air slows down and the air's
Answer: (C) pressure increases. [92.5% picked]
Why: Video Discussion
Problem 8:
When a rocket leaves earth's atmosphere, there is no longer any air near it. Is the rocket still able to obtain forward thrust and, if so, what is pushing it forward?
Answer: (D) Yes, its exhaust gases push it forward. [89.4% picked]
Why: Video Discussion
Problem 9:
You are a pole-vaulter and, having just cleared the bar at your personal best height, you begin to fall toward the thick foam rubber pad far below. When during your descent do you first stop accelerating downward?
Answer: (A) When you pass through equilibrium in the pad for the first time. [90.3% picked]
Why: Video Discussion
Problem 10:
As a soccer ball travels from the kicker to the goal, air approaches the front of the ball and they interact. The ball loses much of its forward momentum during its flight because
Answer: (C) the air at the front of the ball is higher than atmospheric pressure while the air behind the ball is approximately atmospheric pressure. [71.7% picked]
Why: Video Discussion
Problem 11:
When you try to balance a pencil on its sharpened point, it invariably tips over. That's because the upright pencil
Answer: (B) has an unstable equilibrium and it accelerates away from that equilibrium after the slightest disturbance. [95.6% picked]
Why: Video Discussion
Problem 12:
Two toy cars roll off a level table side-by-side at the same time and in the same direction. The cars soon hit the level floor below the table. The orange car weighs twice as much as the green car, but both cars were traveling at the same horizontal speed when they left the table. In this situation,
Answer: (A) the two cars hit the floor at approximately the same time and the same distance from the table. [69.9% picked]
Why: Video Discussion
Problem 13:
You want to help a seriously ill person, but the door to their room is locked. To have the best chance of breaking the door open, you run toward the door (to accumulate forward momentum) and then hit the door with your
Answer: (D) hard feet and jump strongly so that you end up moving backward at the same speed you had before hitting the door. [50.4% picked]
Why: Video Discussion
Problem 14:
An airplane is cruising horizontally at 30,000 feet and is traveling at constant velocity. The overall force that airplane exerts on the air points
Answer: (D) straight downward. [65.9% picked]
Why: Video Discussion
Problem 15:
If the airflow passing over the top of an airplane wing suddenly breaks away from the surface of the wing and forms a turbulent wake, the airplane will experience a rise in
Answer: (D) pressure drag and a decrease in lift. [57.1% picked]
Why: Video Discussion
Problem 16:
You are designing a chair for a museum. While your chair will be a work of art, it must also be practical and it mustn't tip over easily. To ensure that it stays upright, you design it so that its
Answer: (B) center of gravity always rises if you tip it. [62.8% picked]
Why: Video Discussion
Problem 17:
You are working in a pizza parlor. You toss a spinning disk of pizza dough into the air. As the dough stretches outward and the flying disk becomes wider, what happens to the disk's angular velocity?
Answer: (D) It decreases. [79.6% picked]
Why: Video Discussion
Problem 18:
You hold an ordinary helium-filled rubber balloon motionless in a small room filled with helium gas and then release the balloon. That balloon
Answer: (A) descends to the floor. [64.2% picked]
Why: Video Discussion
Problem 19:
The chemical bond that causes two oxygen atoms to cling together as an oxygen molecules is
Answer: (A) a deficit of energy—the work needed to separate those two atoms from one another. [43.4% picked]
Why: Video Discussion
Problem 20:
You leave the bathroom window open on a cold day and find that your cloth towel, the metal towel rack, and the ceramic tile wall are all at 50 °F. When those three objects are touching one another, heat
Answer: (D) does not flow between them. [73.0% picked]
Why: Video Discussion
Problem 21:
Firefighters are battling a fire on the 10th floor of an apartment building. When they stand on the ground, their fire hose can only shoot the water steadily up to the 8th 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
Answer: (D) 8th floor. [92.5% picked]
Why: Video Discussion
Problem 22:
If a skyscraper supplied water to all of its floors through a single vertical pipe,
Answer: (B) the water pressure would be much greater at the lower floors than at the upper floors. [91.6% picked]
Why: Video Discussion
Problem 23:
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
Answer: (A) give the satellite such a large horizontal speed that the falling satellite arcs endlessly around the earth rather than descending to the ground. [76.5% picked]
Why: Video Discussion
Problem 24:
You are swinging an open can of paint around in a horizontal circle at a steady speed. Your friends watch as the can circles from north to west to south to east to north, over and over again. As the can reaches its northern position, you accidentally let go of the can and the paint splatters one of your friends. In which direction did the paint travel after you released it?
Answer: (A) Toward the west. [49.1% picked]
Why: Video Discussion
Problem 25:
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
Answer: (B) downward at more than the acceleration due to gravity. [63.3% picked]
Why: Video Discussion
Problem 26:
You are playing miniature golf with friends and, as part of one hole, your golf ball rolls on a series of different ramps. The ramps are all flat surfaces, but they have different steepnesses. As the ball moves onto steeper and steeper ramps, the ball's
Answer: (B) acceleration becomes greater. [60.6% picked]
Why: Video Discussion
Problem 27:
As water flows upward in a vertical pipe that has a uniform diameter, the water's gravitational potential energy increases,
Answer: (C) its pressure potential energy decreases, but its kinetic energy remains constant. [73.0% picked]
Why: Video Discussion
Problem 28:
On a cold morning, you seal your empty plastic water bottle and thus trap the air inside it. Later in the day, the bottle and its contents are much warmer and the elastic sides of the bottle are now stretched outward. The bottle's volume has increased. Based on these changes, you can be certain that the air pressure inside the bottle has
Answer: (D) increased, but the density inside the bottle has decreased. [86.3% picked]
Why: Video Discussion
Problem 29:
You are at a barbeque and the bottle of hot sauce is almost empty. You put the cap on the bottle and swing it rapidly in a circle with its cap end pointing outward. The remaining sauce collects just inside the cap and you are able to extract enough to spice up your vanilla ice cream. This technique works because
Answer: (C) the bottle's rapid inward acceleration leaves the hot sauce behind so that it drifts toward the cap end of the bottle. [94.7% picked]
Why: Video Discussion
Problem 30:
You're at the lake and watch two children jump off a dock at the same time. They both kick equally hard during their jumps, but one child jumps mostly upward while the other child jumps mostly forward. After they leave the dock,
Answer: (C) the child who jumps forward reaches the water before the child who jumps upward. [93.8% picked]
Why: Video Discussion