Physics 1060 - Spring 2014 - Midterm 1, Part B - Posted Version

Problem 1:

You are about to push two coins off a horizontal table simultaneously, a US quarter (big coin) and US dime (little coin). They start side-by-side near the edge of the table and you push them equally hard for equal times. Off they go! Which of the following choices correctly describes what happens to the coins?

(A) They hit the floor at the same time, but the dime hits the ground farther from the table than does the quarter.

(B) The dime hits the floor first, although both coins hit the floor at the same distance from the table.

(D) They hit the floor at the same time and at the same distance from the table.

Problem 2:

You are standing on the level floor in the middle of a room and decide to walk toward the door. As you accelerate horizontally toward the door, what force(s) is the floor exerting on you?

(A) An upward support force equal in amount to your weight and a frictional force directed toward the door.

(B) A support force directed toward the door.

(D) A frictional force directed toward a point above the door.

Problem 3:

A meteor streaks through the sky at amazing speed. It cannot stop quickly because it entered the atmosphere carrying an enormous portion of a specific physical quantity and must transfer all of that quantity to other objects in order to stop. What is that physical quantity the meteor is carrying?

(A) mass

(B) momentum

(D) force

Problem 4:

You are skating with a friend. You give your friend a push as your friend is moving away from you. During that push, the force you exerted on your friend was

(A) equal to the force your friend exerted on you.

(B) larger in amount than the force your friend exerted on you.

(D) equal in amount but opposite in direction to the force your friend exerted on you.

Problem 5:

Your cellphone battery died, so you have to return to the real world. You throw a ball upward and it rises for 2 seconds to a peak height of about 20 meters (66 feet) above your hand. After only 1 second of rising, how high above your hand was the ball?

(A) Approximately 10 meters

(B) Approximately 11 meters

(D) Approximately 5 meters

Problem 6:

Your clothes emerge from the dryer with lots of static electricity. As you pull a positively charged sock away from the negatively charged jacket it was clinging to, what happens to the sock? [Assume that you did not exchange charge with anything while separating the two objects.]

(A) The sock’s voltage increases.

(B) The sock’s electric charge decreases.

(D) The sock’s voltage decreases.

Problem 7:

The floor of a restaurant consists of hard ceramic tiles with soft wooden spacers between them. Two identical empty bottles slide off a table and fall to the floor. One bottle hits a ceramic tile and shatters. The other bottle hits a wooden insert and survives. Assume both bottles stopped completely when they hit the floor. Why did the two bottles have different fates?

(A) The bottle that hit the wooden insert transferred more momentum to the floor than the other bottle.

(B) The two transferred equal momentums to the floor, but the bottle that the wooden insert transferred its momentum to the floor over a shorter period of time and with a smaller force than the other bottle.

(D) The two transferred equal momentums to the floor, but the bottle that hit the wooden insert transferred its momentum to the floor over a longer period of time and with a smaller force than the other bottle.

Problem 8:

You walk on a carpet and accumulate a large static charge. If you reach out to a doorknob with your finger, you'll receive a strong shock. Instead, you reach out to the doorknob with a sharp metal needle in your hand, pointing that needle toward the doorknob. As the needle moves toward the doorknob, you receive

(A) no shock at all.

(B) a strong shock anyway (the same as without the pin).

(D) a moderately strong shock (slightly less than without the pin).

Problem 9:

You are playing on a trampoline. At this moment, you are pushing downward on the trampoline's surface with a force that is greater in amount than your weight. What is happening to you?

(A) You are accelerating upward.

(B) You are accelerating downward.

(D) You are moving downward (the direction of your velocity is downward).

Problem 10:

Why is a hammer able to pound a nail upward into the ceiling?

(A) When the moving hammer hits the nail, it transfers all of its upward momentum to the nail in a very short period of time and thus with an enormous force. That impact force pushes the nail into the ceiling.

(B) Despite the upward motion of the hammer, its weight still pushes it forward as it moves. Because the hammer weighs so much more than the nail, it pushes much harder on the nail than the nail pushes on it. That force difference pushes the nail into the ceiling.

(C) Because the hammer has so much more mass than the nail, the hammer pushes harder on the nail than the nail pushes on the hammer. That force difference pushes the nail into the ceiling.

(D) The moving hammer carries an enormous force with it. When the hammer impacts the nail, it transfers that force to the nail. Because the tiny nail has all that force in it, it can easily push itself into the ceiling.

Problem 11:

You have a shopping cart filled with groceries and you want to roll that cart up a ramp. While your cart is on the ramp, it experiences a downhill ramp force of 10 pounds-force (about 44 newtons). For your cart to move uphill on the ramp at constant velocity, what force must you exert on the cart with your hands? [Neglect any friction and assume you push the cart only along (parallel to) the ramp]

(A) You must exert an uphill force greater than 10 pounds-force.

(B) You must exert an uphill force less than 10 pounds-force, but greater than zero.

(D) You must exert an uphill force of 10 pounds-force.

Problem 12:

You are twisting the lid of a jar and so is friction. The torque that you exert on the lid points in the direction that opens the lid (your torque points out of the jar), while the torque that friction exerts on the lid points in the direction that closes the lid (friction's torque points into the jar). If your torque on the lid is slightly greater in amount than friction's torque on the lid, how is the lid moving?

(A) The lid is undergoing angular acceleration in the direction that opens the lid (the lid's angular acceleration points out of the jar).

(B) The lid's angular velocity points in the direction that closes the lid (the lid's angular velocity points into the jar).

(C) The lid's angular velocity points in the direction that opens the lid (the lid's angular velocity points out of the jar).

(D) The lid is undergoing angular acceleration in the direction that closes the lid (the lid's angular acceleration points into the jar).

Problem 13:

In your self-defense class, you practice throwing punches by hitting a massive bag that is hanging from the ceiling. The bag swings alternately toward you and away from you as you practice. To transfer (positive) energy to the bag most effectively, when during its swing should you punch the bag?

(A) When it is closest to you.

(B) While it is moving away from you.

(D) When it is farthest from you.

Problem 14:

You are holding two boxes, one in each hand, and both boxes are motionless. Although the boxes have equal weights, the blue box is taller and the red box is wider. Which of the following statements is correct?

(A) You are doing less work on the blue box than on the red box.

(B) You are doing the same non-zero work on each box.

(D) You are doing more work on the blue box than on the red box.

Problem 15:

A piece of tape is stuck to a glass window. Together, they are electrically neutral. You carefully peel the tape off the window and discover that the tape has a negative electric charge. What is the charge of the window? [Assume that you did not exchange charge with anything while peeling the tape from the window.]

(A) Peeling the tape from the window leaves the window with a random charge, which can be positive, negative, or neutral.

(B) The window is electrically neutral.

(D) The window has a positive electric charge.

Problem 16:

During a storm, a high-voltage electric power line falls on the car you are driving and it transfers a dangerous amount of positive charge to your car. The car’s rubber tires prevent that charge from flowing into the ground. When everything reaches equilibrium, where is the car’s charge located?

(A) It is on both the outside and inside surfaces of the car.

(B) It is distributed uniformly throughout the car’s metal components.

(D) It is on the inside surface of the car.

Problem 17:

You're at the lake and watch two children jump off a dock. They jump at the same time and at the same speed, but the boy jumps mostly upward while the girl jumps mostly forward. After they leave the dock,

(A) the two children reach the water at the same moment, but the girl travels farther from the dock than does the boy.

(B) girl reaches the water before the boy.

(D) boy reaches the water before the girl.

Problem 18:

When you're using your cellphone on the beach, in which direction is current flowing through its battery and through its computer?

(A) Current flows toward higher voltage through the battery and toward higher voltage through the computer.

(B) Current flows toward lower voltage through the battery and toward higher voltage through the computer.

(D) Current flows toward higher voltage through the battery and toward lower voltage through the computer.

Problem 19:

You are sprinting forward down the lawn (toward Old Cabell Hall), late for an audition, and suddenly remember that you left your student ID on the Rotunda steps. You need to reverse directions in a hurry. Fortunately, the Statue of Homer is just ahead of you. You grab Homer's rock solid arm and swing around him like Spiderman, not even touching the ground. When you let go of Homer, you are heading swiftly backward up the lawn (toward the Rotunda). During your encounter with Homer, you transferred to Homer

(A) more forward momentum than you had, but almost zero energy.

(B) nearly all of your forward momentum, but almost zero energy.

(D) nearly all of your energy, but almost zero momentum.

Problem 20:

You are a firefighter and are in a parade to celebrate your daring rescue of two children from a burning building. The town's main street has a gradual slope and your firetruck is traveling uphill along that street and moving at constant velocity. You are perched at the top of the firetruck's extended ladder. The overall force that the ladder is exerting on you points in which direction?

(A) Uphill (in the direction the firetruck is traveling)

(B) Between upward and uphill (toward a point somewhat above the uphill end of the main street)

(D) Upward

Problem 21:

The horizontal floor and ceiling of a factory are made of metal. The voltage of the ceiling is 100 volts and the voltage of the floor is 0 volts. What is the direction of the electric field at the exact center of the room?

(A) The electric field in the center of the room is zero, so it has no direction.

(B) Horizontal

(D) Down

Problem 22:

A toy top is initially free of external torques. You exert a torque on the top and the top exerts an equal but oppositely directed torque on you. How does the top move?

(A) The top is motionless.

(B) The top undergoes angular acceleration in the direction of your torque on it.

(D) The top has a constant angular velocity, which may be zero.

Problem 23:

In what circumstance can an isolated dust particle in the air have half (1/2) the charge of a proton (the positively charged nucleus of a hydrogen atom)?

(A) After it has transferred an equal amount of negative charge to another dust particle.

(B) Never.

(D) After it has received that amount of positive charge from another dust particle.

Problem 24:

Your friends are picking up a big block of ice for a party. They park their pickup truck on level ground and put the block of ice in the middle of the truck's horizontal bed (its load-carrying compartment). They leave the back of the truck open. Assume that the ice is perfectly slippery and experiences no frictional forces. What happens to the block of ice when they drive the truck forward?

(A) The truck's horizontal bed exerts a forward support force on the ice and the ice moves with the truck.

(B) As the truck accelerates forward, the motionless ice remains motionless. The truck leaves the ice behind and that ice falls to the ground.

(D) As the truck moves forward, the ice accelerates backward and falls to the ground.

Problem 25:

An Olympic skier completes two full rotations (a "720") as she arcs through the air after going off a jump. To slow her angular velocity as she approaches her landing, she extends her arms outward from her center of mass. Why does extending her arms slow her rotation? [Neglect any effects due to the air.]

(A) The torque of her rotation is distributed evenly on her body as she leaves the jump. As she extends her arms, however, that torque flows outward and the core of her body must rotate more slowly.

(B) As she extends her arms, the torque she experiences increases and she undergoes angular deceleration so that her angular velocity decreases.

(C) Since she is free of external torques, her angular momentum is constant. As she extends her arms, and thereby increases her rotational mass, her angular velocity must decrease to keep her angular momentum constant.

(D) The skier must exert a torque on herself to keep herself rotating. She does this primarily with her hands. As she extends her arms, the amount of torque she exerts on herself decreases and her rotation slows.

Problem 26:

You are at the gym, exercising on a step machine. You have one foot on each of the machine's pedals and you move those pedals up and down as you step. The pedals always push upward on your feet, although they push harder while moving downward than while moving upward. When during this exercise are you transferring energy to the step machine?

(A) When the pedals are accelerating.

(B) As the pedals move upward.

(D) As the pedals move either upward or down.

Problem 27:

You are watching a football game. The quarterback throws the football in a long, smooth arc to a distant receiver, who catches the football. While the football is traveling in its arc and no one is touching it, when is that football traveling slowest (has the smallest speed)?

(A) Just before the receiver catches the football.

(B) When it reaches its peak height during that arc.

(D) Just after the quarterback has thrown the football.

Problem 28:

A xerographic copier uses a very thin wire with a large positive voltage to spray electric charges onto the surface of its photoconductor. The thin wire

(A) heats up quickly and boils off electric charge onto the surface of the photoconductor.

(B) is able to move charge quickly enough to produce finely detailed light and dark spots on the copies.

(C) has a weak electric field near it and that weak field easily permits the transfer of charge from the wire to the surface of the photoconductor.

(D) has a strong electric field near it and that strong field pushes charge from the wire onto air molecules.

Problem 29:

An earthquake has tilted the local ice rink so that the ice surface is now a frictionless ramp. As a hockey puck slides across the ice, how does the puck move?

(A) The puck experiences a constant downhill acceleration.

(B) The puck has a constant downhill velocity.

(D) The puck travels slower (less speed) when it moves uphill than it does when it moves downhill.

Problem 30:

Why does a negatively charged balloon stick to an electrically neutral wall? [Assume the wall is an electric insulator.]

(A) As the balloon approaches the wall, it transfers half of its negative charge to the wall. The two portions of charge attract one another, binding the balloon to the wall.

(B) As the negatively charged balloon approaches the wall, the wall develops a negative charge. The like charged balloon and wall then attract one another.

(C) The balloon’s negative charge causes charges in the wall to shift slightly—its positive charges moving slightly closer to the balloon than its negative charges. The electrically polarized wall then attracts the negatively charged balloon.

(D) As the negatively charged balloon approaches the wall, the wall develops a positive charge. The oppositely charged balloon and wall then attract one another.