Physics 1060 - Spring 2018 - Midterm 1 Exam - Posted Version with Solutions
Problem 1:
Running on soft dry sand is exhausting, so you switch to running on hard wet sand. The hard wet sand removes less energy from you because
(A) it stops the downward motion of your foot faster and thus absorbs less of your momentum. [17.0% picked]
(B) its water content gives it more mass and that prevents it from absorbing energy. [1.7% picked]
(C) it pushes up on your foot just as hard as your foot pushes on it, unlike the soft dry sand. [9.1% picked]
(D) it barely moves downward as you push downward on it, so you do almost zero work on it. [72.2% picked]
Answer: (D) it barely moves downward as you push downward on it, so you do almost zero work on it. [72.2% picked]
Why: TBA
Problem 2:
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
(A) has a weak electric field near it and that weak field easily permits the transfer of charge from the wire to surface of the photoconductor. [3.5% picked]
(B) heats up quickly and boils off electric charge onto the surface of the photoconductor. [1.3% picked]
(C) is able to move charge quickly enough to produce finely detailed light and dark spots on the copies. [0.9% picked]
(D) has a strong electric field near it and that strong field pushes charge from the wire onto air molecules. [94.3% picked]
Answer: (D) has a strong electric field near it and that strong field pushes charge from the wire onto air molecules. [94.3% picked]
Why: TBA
Problem 3:
There are two metal balls on your desk, one on the left and one on the right (see figure). Someone has attached a battery to those balls, so the voltage of the left ball is +5 volts and the voltage of the right ball is –5 volts. Midway between the two balls, the electric field points
(A) upward. [3.5% picked]
(B) downward. [1.7% picked]
(C) toward the right. [87.8% picked]
(D) toward the left. [7.0% picked]
Answer: (C) toward the right. [87.8% picked]
Why: TBA
Problem 4:
At this moment in time, a water bottle is touching only one thing: the top of a table. The downward force the water bottle is exerting on the table right now
(A) is equal to the water bottle's weight. [70.0% picked]
(B) is greater than, less than, or equal to the water bottle's weight, depending on the situation. [29.6% picked]
(C) is less than the water bottle's weight. [0.0% picked]
(D) is greater than the water bottle's weight. [0.4% picked]
Answer: (B) is greater than, less than, or equal to the water bottle's weight, depending on the situation. [29.6% picked]
Why: TBA
Problem 5:
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) Never. [83.5% picked]
(B) After it has transferred an equal amount of negative charge to another dust particle. [7.8% picked]
(C) After it has received that amount of positive charge from another dust particle. [3.0% picked]
(D) After a larger dust particle with the charge of one (1) proton breaks into two equal halves. [5.7% picked]
Answer: (A) Never. [83.5% picked]
Why: TBA
Problem 6:
As shown in the figure below, a sharp metal pin has a voltage of +1000 volts and it points toward a wide metal surface with a voltage of –1000 volts. Where in this system can you find a position where the voltage is 0 volts?
(A) There is no position in this system at which the voltage is 0 volts. [27.0% picked]
(B) At the midway point. [23.5% picked]
(C) To the left of the midway point. [12.6% picked]
(D) To the right of the midway point. [37.0% picked]
Answer: (D) To the right of the midway point. [37.0% picked]
Why: TBA
Problem 7:
To win a stuffed animal at the state fair, you simply need to drop a glass marble onto a stationary glass plate and have the marble come to rest on that plate. Unfortunately, when the marble hits the plate, it bounces upward because the marble
(A) retains essentially all of its momentum but transfers a large amount of energy to the plate. [7.0% picked]
(B) retains essentially all of its energy and momentum. [10.0% picked]
(C) retains essentially all of its energy but transfers a large amount of momentum to the plate. [79.1% picked]
(D) transfers a large amount of momentum and energy to the plate. [3.9% picked]
Answer: (C) retains essentially all of its energy but transfers a large amount of momentum to the plate. [79.1% picked]
Why: TBA
Problem 8:
During a storm, a high-voltage electric power line falls on your car and transfers a dangerous amount of positive charge to the car's metal structure. The car's rubber tires prevent that charge from flowing into the ground. When everything reaches equilibrium, where is the metal car's charge located?
(A) On both the outside and inside surfaces of the car. [0.9% picked]
(B) On the inside surface of the car. [0.9% picked]
(C) On the outside surface of the car. [86.5% picked]
(D) Distributed uniformly throughout the car's metal components. [11.7% picked]
Answer: (C) On the outside surface of the car. [86.5% picked]
Why: TBA
Problem 9:
Your new Cavalier bobble-head comes protected by packing peanuts. When you remove those peanuts from the box, they cling to everything. If a peanut is negatively charged, why does it stick to a neutral wall?
(A) The peanut transfers all of its negative charge to the wall, so the neutral peanut and charged wall attract one another. [0.0% picked]
(B) The peanut's negative charge electrically polarizes the wall, so the charged peanut and polarized wall attract one another. [95.7% picked]
(C) The peanut transfers half its negative charge to the wall, so the charged peanut and charged wall attract one another. [0.0% picked]
(D) The peanut's negative charge causes the wall to become positively charged, so the charged peanut and charged wall attract one another. [4.3% picked]
Answer: (B) The peanut's negative charge electrically polarizes the wall, so the charged peanut and polarized wall attract one another. [95.7% picked]
Why: TBA
Problem 10:
You toss a book onto your desk. The book slides forward but quickly slows to a stop. What became of the book's initial kinetic energy?
(A) The book did (positive) work on the desk, so the book's energy was transferred to the desk. [4.4% picked]
(B) The book's energy was transferred by gravity to the Earth. [0.4% picked]
(C) The desk did negative work on the book, so the book's energy disappeared completely. [0.9% picked]
(D) The book's energy became thermal energy in the two sliding surfaces. [94.3% picked]
Answer: (D) The book's energy became thermal energy in the two sliding surfaces. [94.3% picked]
Why: TBA
Problem 11:
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, the
(A) two children reach the water at the same moment, but the girl travels farther from the dock than does the boy. [10.0% picked]
(B) boy reaches the water before the girl. [1.3% picked]
(C) girl reaches the water before the boy. [88.7% picked]
(D) two children reach the water at the same moment and at the same distance from the dock. [0.0% picked]
Answer: (C) girl reaches the water before the boy. [88.7% picked]
Why: TBA
Problem 12:
The electric field near a negative charge points
(A) toward the negative charge and becomes weaker with increasing distance from the negative charge. [77.4% picked]
(B) toward the negative charge and does not depend on the distance from the negative charge. [4.3% picked]
(C) away from the negative charge and does not depend on the distance from the negative charge. [0.4% picked]
(D) away from the negative charge and becomes weaker with increasing distance from the negative charge. [17.8% picked]
Answer: (A) toward the negative charge and becomes weaker with increasing distance from the negative charge. [77.4% picked]
Why: TBA
Problem 13:
A snowboarder moves swiftly off a jump and is doing crazy acrobatics high above the ground. While the snowboarder is not touching anything and neglecting any effects due to the air, what aspect of the snowboarder's motion must remain constant?
(A) The snowboarder's angular momentum. [83.9% picked]
(B) The snowboarder's momentum. [7.4% picked]
(C) The snowboarder's velocity. [4.3% picked]
(D) The snowboarder's angular velocity. [4.3% picked]
Answer: (A) The snowboarder's angular momentum. [83.9% picked]
Why: TBA
Problem 14:
You like to live dangerously, so you drop your cell phone out the window near the top of a tall building. It will hit the ground in 4 seconds if you don't do something immediately. You race downstairs to an open window and catch the phone after it has fallen for 2 seconds. If it had fallen for 4 seconds, it would have traveled the entire distance to the ground. After falling for just 2 seconds, what distance had it traveled?
(A) It traveled about 8 inches less than 1/2 of the distance to the ground. [7.8% picked]
(B) It traveled 3/4 of the distance to the ground. [5.7% picked]
(C) It traveled 1/2 of the distance to the ground. [5.2% picked]
(D) It traveled 1/4 of the distance to the ground. [81.3% picked]
Answer: (D) It traveled 1/4 of the distance to the ground. [81.3% picked]
Why: TBA
Problem 15:
You're having trouble loosening a rusty bolt with a short wrench, so you borrow a long wrench from your neighbor. Exerting only a modest force on the handle of this new wrench easily unscrews the bolt. The long wrench helps because it
(A) has a larger mass so that its inertia allows you to overcome the bolt's velocity and accelerate it around in a circle. [0.4% picked]
(B) has a larger acceleration and a larger mass, so the force it produces is larger, according to the equation F=ma. [0.0% picked]
(C) has a larger rotational mass so that it develops a great deal of angular momentum when you exert a force on it. [13.0% picked]
(D) allows you to exert your force farther from the center of rotation, so that you produce a larger torque on the bolt. [86.5% picked]
Answer: (D) allows you to exert your force farther from the center of rotation, so that you produce a larger torque on the bolt. [86.5% picked]
Why: TBA
Problem 16:
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 any charge with the tape or window.]
(A) Peeling the tape from the window leaves the window with a random charge, which can be positive, negative, or neutral. [1.3% picked]
(B) The window has a positive electric charge. [90.0% picked]
(C) The window is electrically neutral. [7.4% picked]
(D) The window has a negative electric charge. [1.3% picked]
Answer: (B) The window has a positive electric charge. [90.0% picked]
Why: TBA
Problem 17:
You are standing in the middle of motionless bus, with a skateboard under your feet. The light turns green and the bus begins to move forward. Why do you find yourself rolling toward the back of the bus?
(A) The skateboard prevents the bus from pushing you forward, so you remain inertial and the accelerating bus leaves you behind. [89.1% picked]
(B) The bus transfers backward momentum to you with the help of the skateboard. [3.9% picked]
(C) The bus exerts torques on the skateboard wheels and the wheels exert torques on you. [3.0% picked]
(D) The bus pushes the bottoms of the skateboard wheels forward, so the tops of the wheels push you backward. [3.9% picked]
Answer: (A) The skateboard prevents the bus from pushing you forward, so you remain inertial and the accelerating bus leaves you behind. [89.1% picked]
Why: TBA
Problem 18:
You are trying to open a jar of honey and find that the lid is stuck. You are twisting the lid in the opening direction, but it won't budge. To succeed in opening the lid, what must you do?
(A) You must exert a larger torque on the lid in the opening direction than the jar is exerting on the lid in the closing direction. [80.0% picked]
(B) You must exert a larger torque on the lid than the lid is exerting on you. [14.8% picked]
(C) The angular velocity of your hand must be greater than the angular velocity of the lid. [0.9% picked]
(D) The angular acceleration of your hand must be greater than the angular acceleration of the lid. [4.3% picked]
Answer: (A) You must exert a larger torque on the lid in the opening direction than the jar is exerting on the lid in the closing direction. [80.0% picked]
Why: TBA
Problem 19:
A juggler tosses a ball straight up in the air. At the moment the ball reaches its peak altitude, what are its velocity and acceleration?
(A) The ball's velocity is zero and its acceleration is zero. [0.9% picked]
(B) The ball's velocity is zero and its acceleration is downward. [95.2% picked]
(C) The ball's velocity is downward and its acceleration is zero. [3.9% picked]
(D) The ball's velocity is downward and its acceleration is upward. [0.0% picked]
Answer: (B) The ball's velocity is zero and its acceleration is downward. [95.2% picked]
Why: TBA
Problem 20:
Before its launch from Earth, the Mars rover Curiosity had a mass of 899 kilograms and it weighed 1982 pounds. Now that it is on Mars, Curiousity's mass
(A) is different, but its weight remains unchanged. [3.0% picked]
(B) is different and its weight is different. [1.3% picked]
(C) remains unchanged, but its weight is different. [94.3% picked]
(D) remains unchanged and its weight remains unchanged. [1.3% picked]
Answer: (C) remains unchanged, but its weight is different. [94.3% picked]
Why: TBA
Problem 21:
You are arm-wrestling a friend. While you are gradually winning the competition, compare the torque that your arm exerts on your friend's arm to the torque your friend's arm exerts on your arm.
(A) The two torques are equal. [1.3% picked]
(B) The torque you exert on your friend is greater in amount than the torque your friend exerts on you. [79.6% picked]
(C) Those two torques are equal in amount but opposite in direction. [18.7% picked]
(D) The torque you exert on your friend is less in amount than the torque your friend exerts on you. [0.4% picked]
Answer: (C) Those two torques are equal in amount but opposite in direction. [18.7% picked]
Why: TBA
Problem 22:
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? [Neglect air effects.]
(A) It remains constant because angular velocity is conserved. [10.0% picked]
(B) It remains constant because no torque acts on the disk. [9.6% picked]
(C) It decreases. [72.6% picked]
(D) It increases. [7.8% picked]
Answer: (C) It decreases. [72.6% picked]
Why: TBA
Problem 23:
Which of these vehicles is accelerating?
(A) An elevator moving downward and experiencing a net force of zero. [20.9% picked]
(B) A train that is moving at a steady speed around a curved track. [71.3% picked]
(C) A wagon moving up a smooth, straight ramp at a steady speed. [7.0% picked]
(D) An elevator that is motionless and experiencing a net force of zero. [0.9% picked]
Answer: (B) A train that is moving at a steady speed around a curved track. [71.3% picked]
Why: TBA
Problem 24:
You are pulling a toy wagon up a ramp that rises vertically 1 meter for every 12 meters you travel uphill along its surface (see figure). If you let go of the wagon, how will it move? [neglect friction and effects due to the air]
(A) It will accelerate downhill at 12 times the acceleration due to gravity. [2.2% picked]
(B) It will accelerate downhill at 1/6th the acceleration due to gravity. [5.2% picked]
(C) It will move downhill at a constant velocity. [4.3% picked]
(D) It will accelerate downhill at 1/12th the acceleration due to gravity. [88.3% picked]
Answer: (D) It will accelerate downhill at 1/12th the acceleration due to gravity. [88.3% picked]
Why: TBA
Problem 25:
Your friend has just tossed a raw egg to you. To catch the egg without breaking it, you must move your hand with the egg so that you gradually bring it to a stop. Why does moving your hand in the direction of the egg's velocity help you catch the egg intact?
(A) It reduces the frictional force the egg exerts on you when you grab hold of it. [1.3% picked]
(B) It reduces the mass of the egg and makes it easier for you to accelerate the egg to a stop. [0.4% picked]
(C) It allows the egg to give you its energy and forward momentum with a smaller force exerted over a larger distance and longer time. [93.0% picked]
(D) It reduces the difference between the momentum of the egg and the momentum of your hand. [5.2% picked]
Answer: (C) It allows the egg to give you its energy and forward momentum with a smaller force exerted over a larger distance and longer time. [93.0% picked]
Why: TBA
Problem 26:
You are using a string to lift a heavy picnic basket up to your treehouse. Alas, the string isn't strong enough for the job. The picnic basket remains motionless on the ground, even though you are moving the portion of string in your hand upward, and the string breaks. Breaking the string required energy and that energy was provided by
(A) your hand. [85.7% picked]
(B) both your hand and the picnic basket. [6.5% picked]
(C) the picnic basket. [3.9% picked]
(D) the string's elastic potential energy. [3.9% picked]
Answer: (A) your hand. [85.7% picked]
Why: TBA
Problem 27:
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
(A) a forward horizontal force that remains constant all the way to home plate. [7.0% picked]
(B) no horizontal force in the forward direction. [87.4% picked]
(C) a forward horizontal force that diminishes gradually as the ball approaches home plate. [5.2% picked]
(D) a forward horizontal force until it reaches the midpoint of its trip to home plate and then a backward horizontal force for the remainder of its trip. [0.4% picked]
Answer: (B) no horizontal force in the forward direction. [87.4% picked]
Why: TBA
Problem 28:
You are pushing a desk across a tile floor. The desk is moving in a straight line at a steady speed. Compare the force you exert on desk to the frictional force the floor exerts on the desk. [Assume that those two forces are the only horizontal forces acting on the desk.]
(A) The force you exert desk is greater in amount than the frictional force the floor exerts on the desk. [16.1% picked]
(B) The force you exert desk is less in amount than the frictional force the floor exerts on the desk. [0.0% picked]
(C) The force you exert desk is equal in amount but opposite in direction to the frictional force the floor exerts on the desk. [69.6% picked]
(D) The force you exert desk is equal to the frictional force the floor exerts on the desk. [14.3% picked]
Answer: (C) The force you exert desk is equal in amount but opposite in direction to the frictional force the floor exerts on the desk. [69.6% picked]
Why: TBA
Problem 29:
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) a moderately strong shock (slightly less than without the pin). [1.7% picked]
(B) a strong shock anyway (the same as without the pin). [3.5% picked]
(C) an extra-strong shock (significantly more than without the pin). [4.8% picked]
(D) no shock at all. [90.0% picked]
Answer: (D) no shock at all. [90.0% picked]
Why: TBA
Problem 30:
One end of a AAA battery has a voltage of +0.75 volts and the other end has a voltage of –0.75 volts. Suppose you have a small positive charge located at 0 volts. What work is required to move that positive charge to each of end of the battery?
(A) Negative work is required to move the charge to the +0.75 volts end and positive work is required to move the charge to the –0.75 volts end. [30.4% picked]
(B) Positive work is required to move the charge to the +0.75 volts end and negative work is required to move the charge to the –0.75 volts end. [53.5% picked]
(C) Negative work is required to move the charge to the +0.75 volts end and negative work is required to move the charge to the –0.75 volts end. [3.0% picked]
(D) Positive work is required to move the charge to the +0.75 volts end and positive work is required to move the charge to the –0.75 volts end. [13.0% picked]
Answer: (B) Positive work is required to move the charge to the +0.75 volts end and negative work is required to move the charge to the –0.75 volts end. [53.5% picked]
Why: TBA
