PHYS 1060 Midterm Exam 1, Spring 2010 - Solutions
Problem 1:
When a modern car crashes into a tree and comes to an abrupt stop, the driver's face and chest collide with an air bag rather than with the steering wheel. The driver's chances of serious injury are reduced by hitting the air bag rather than the steering wheel because the driver transfers
Answer: (B) the same amount of momentum to the air bag as he would to the steering wheel, but he does so with a smaller force over a longer period of time. [95.5% picked]
Why: Video Discussion
Problem 2:
A van de Graaff static generator has a huge amount of electric charge on its ball-shape top. If you move your hand slowly toward the ball, a spark will occur when your hand is about 12 inches from the ball. If you hold a sharp metal needle in your hand, aimed at the ball, and move your hand slowly toward the ball,
Answer: (D) no spark will occur. [84.0% picked]
Why: Video Discussion
Problem 3:
Two hikers carry identical backpacks from a nature center to the top of a nearby mountain. One hiker takes the short, steep trail to the top and arrives first. The second hiker takes the long, gradual trail to the top and arrives second. Which hiker did the most work on his backpack?
Answer: (B) Neither. They did equal amounts of work on their backpacks. [91.8% picked]
Why: Video Discussion
Problem 4:
You are watching a baseball game and the pitcher has just thrown the ball toward the batter at home plate. Neglect any effects due to the air. Once the ball has left the pitcher's hand and is heading forward toward home plate, it experiences
Answer: (D) no horizontal force in the forward direction. [74.2% picked]
Why: Video Discussion
Problem 5:
A heavy container of orange juice sits on the shelf of your refrigerator's door. That orange juice
Answer: (A) makes it harder to change the door's angular velocity. [93.4% picked]
Why: Video Discussion
Problem 6:
A freestyle skier goes off a jump and does a back flip while separating her legs into a spread eagle. During the time that she is not touching the ground and neglecting any effects due to the air, the one aspect of her motion that is constant is her
Answer: (D) angular momentum. [76.6% picked]
Why: Video Discussion
Problem 7:
You are watching children play a game of tug-o-war with a plastic clothesline. The two teams are pulling at opposite ends of the cord and each team is trying to drag the other team into a mud puddle that lies between them. After a few minutes without progress, the team on the right suddenly pulls hard toward the right. The team on the left has anticipated this threat and is able to keep their end of the rope from moving. The right end of the rope stretches toward the right and the rope breaks. Breaking the rope required energy and that energy was provided by
Answer: (D) the team on the right. [75.8% picked]
Why: Video Discussion
Problem 8:
You are riding a department store escalator from the first floor to the second floor. You are midway between floors and traveling uphill at constant velocity. The force that the escalator exerts on you points
Answer: (B) directly upward. [88.5% picked]
Why: Video Discussion
Problem 9:
You shoot a free throw at the basketball court and the ball travels in an arc toward the hoop. Neglecting any effects due to the air, the net force on the ball when it is midway between you and the hoop
Answer: (C) points straight down. [62.7% picked]
Why: Video Discussion
Problem 10:
When you bounce a tennis ball off a concrete wall, the ball
Answer: (B) retains essentially all of its energy but transfers a large amount of momentum to the wall. [81.1% picked]
Why: Video Discussion
Problem 11:
You walk on a carpet and accumulate a large static charge. You touch a metal pot that's resting on an insulating plastic countertop and transfer some of your charge to the pot. When you remove your hand from the pot, the pot's charge is
Answer: (B) on its outer surface. [91.0% picked]
Why: Video Discussion
Problem 12:
A xerographic copier uses a very thin wire with a large positive voltage to spray electric charges onto the surface of its photoconductor. That thin wire
Answer: (A) has a strong electric field near it and that strong field pushes charge from the wire onto air molecules. [66.4% picked]
Why: Video Discussion
Problem 13:
A flashlight has two wires connecting its battery to its lightbulb. When you turn the flashlight off, the switch disconnects only one of those two wires. Disconnecting one wire stops the lightbulb from glowing because
Answer: (C) current can only flow continuously between the battery and lightbulb when one wire carries it to the lightbulb and another wire returns it to the battery. [98.4% picked]
Why: Video Discussion
Problem 14:
A one-battery flashlight is turned on and is producing light. Current flows through its lightbulb from
Answer: (A) higher voltage to lower voltage. Current flows through its battery from lower voltage to higher voltage. [77.5% picked]
Why: Video Discussion
Problem 15:
A speedboat is pulling a water-skier with a rope and the skier is traveling forward in a straight line path at a constant speed. The net force experienced by the skier
Answer: (D) is zero. [75.0% picked]
Why: Video Discussion
Problem 16:
Two identical children run along a horizontal platform side by side and jump into a swimming pool at the same moment. They both jump equally hard, but one child jumps upward while the other child jumps forward. You watch them fall and see that
Answer: (C) the child who jumped forward reaches the water before the child who jumped upward. [27.0% picked]
Why: Video Discussion
Problem 17:
When it is providing electric power to a lightbulb, a battery uses its chemical potential energy to
Answer: (C) pump positive charge from its negative terminal to its positive terminal. [86.1% picked]
Why: Video Discussion
Problem 18:
You are dragging an old carpet across the floor in a straight line at a steady speed. Which of the following statements about the forces acting on the carpet is correct?
Answer: (C) The amount of force that you're exerting on the carpet must be equal to the amount of force that friction is exerting on it. [33.6% picked]
Why: Video Discussion
Problem 19:
A plastic bag and a glass window are both electrically neutral. You hold the bag with insulating tongs and touch the bag to the window. The bag acquires a positive net charge. As you use the tongs to pull the bag away from the window, the voltage of bag
Answer: (B) increases, but its net charge remains constant. [77.5% picked]
Why: Video Discussion
Problem 20:
You have two bowling balls, one of which weighs twice as much as the other. The balls roll off a horizontal table at the same time and at the same velocity. In this situation, both balls hit the floor
Answer: (D) at approximately the same time and at the same distance from the table. [44.3% picked]
Why: Video Discussion
Problem 21:
You are working out on an elliptical machine at the gym. This particular machine has handles that move away from you as you push them away from you and that move toward you as you pull them toward you. You are transferring energy to those handles
Answer: (D) as you push them away from you and as you pull them toward you. [82.4% picked]
Why: Video Discussion
Problem 22:
A metal birdfeeder hangs from an insulating string and has zero net charge. You rub a toy balloon on your wool sweater, giving the balloon a negative net charge, and hold that balloon near the birdfeeder. The birdfeeder now
Answer: (B) is electrically polarized, with its positive end nearest the balloon. [88.9% picked]
Why: Video Discussion
Problem 23:
A rigid two-blade wind turbine that is experiencing zero net torque
Answer: (C) has a constant angular velocity. [66.4% picked]
Why: Video Discussion
Problem 24:
You bicycling up a hill at constant velocity and the bicycle's pedals are turning at constant angular velocity. Compared to the torque you are exerting on those pedals with your feet, the torque that the bicycle's chain is exerting on those pedals is
Answer: (A) equal in amount but points in the opposite direction. [64.3% picked]
Why: Video Discussion
Problem 25:
You are wearing roller skates. You board a bus and stand motionless in the aisle of the motionless bus. You are facing forward and not touching anything as the bus starts moving forward. You find yourself heading toward the back of the bus. What is causing you to head toward the back of the bus?
Answer: (D) Inertia. [91.4% picked]
Why: Video Discussion
Problem 26:
You are juggling grapefruits and you toss one straight up. Neglect any effects due to the air. After that grapefruit leaves your hand, it experiences
Answer: (A) a constant downward force, both as it rises and as it descends. [77.5% picked]
Why: Video Discussion
Problem 27:
Two children are sitting in a toy wagon. You are pulling that wagon forward on level ground and its speed is increasing. If you are exerting a forward force of 50 newtons on the wagon's handle, the wagon's handle is exerting a backward force of
Answer: (D) 50 newtons on your hand. [77.5% picked]
Why: Video Discussion
Problem 28:
In a famous ice skating trick, a skater begins spinning with her arms out and then pulls her arms tightly against her body. She is then spinning extremely fast on the tip of one skate. Her angular velocity increases because her angular momentum
Answer: (D) is constant but her rotational mass decreases. [88.5% picked]
Why: Video Discussion
Problem 29:
A quick trip down a plastic playground slide has caused a child's fine white-blond hair to begin standing straight up so that she looks like a dandelion puff. During the trip down the slide,
Answer: (A) contact between the slide and the girl transferred electric charge between the slide and girl so that one is positively charged and the other is negatively charged. [81.6% picked]
Why: Video Discussion
Problem 30:
An acorn falls 20 meters from the high branch of an oak tree to the ground. This fall takes about 2 seconds. After it has fallen for only 1 second, the acorn is still falling and is located
Answer: (A) considerably more than 10 meters above the ground. [42.6% picked]
Why: Video Discussion