PHYS 1050 Exam

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

(A) equal in amount but points in the opposite direction.

You are walking a dog on a leash when you come upon a squirrel. The dog suddenly picks up speed and is now pulling you forward with a force of 100 newtons. Neglecting the mass of the leash itself, the backward force you are now exerting on the dog is

(A) 100 newtons

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?

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.

You are dragging a heavy chair across the floor and that chair is moving toward the east at constant velocity. The net force on the chair

zero.

You can open a swinging door (see figure) by pushing it in the middle (Point A, located 1 foot from the hinges) or at the edge farthest from the hinges (Point B, located 2 feet from the hinges). If you exert a 10-newton force on the door, perpendicular to its surface, how will your choice of Point A or Point B affect the door's motion?

(A) Pushing on Point B will cause twice the angular acceleration as compared to pushing on Point A.

Which type(s) of friction convert work into thermal energy?

(A) Sliding friction but not static friction.

You are at a roof party on a 40-story office building, when you accidently knock a rare plant off a ledge. The plant begins to fall and will hit the sidewalk, 122 m (400 ft) below, in 5.0 seconds if you don't catch it. Fortunately, you are exceptionally fast. You race down the stairs to a lower floor and catch the plant through an open window, only 2.5 seconds after it began falling. On which floor did you catch the plant?

(A) The 30th floor, 92 m (300 ft) above the sidewalk.

To win a big prize at the fair or festival, all you have to do is toss a basketball into a bucket a few feet in front of you and have it remain in the bucket. The rigid bucket cannot move and it opens toward you, so the basketball will roll out of it unless the basketball settles in it just right. You try many times to get the basketball to stay in the bucket, but it keeps bouncing out. Why is it so difficult for the basketball to come to rest in the bucket?

(A) The basketball can transfer its momentum to the bucket, but it cannot transfer its energy to the bucket.

Two cars collide gently in a parking lot, damaging their bumpers. How do the two cars' total (combined) momentum and kinetic energy compare before and after the collision? [neglect friction and air effects, and assume the parking lot is otherwise empty and level.]

(A) The cars have the same total momentum before and after, but they have less total kinetic energy after the collision.

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)

Pedaling your bicycle provides power to its rear wheel and propels your bicycle forward. What force(s) is principally responsible for the bicycle's forward acceleration as you pedal your bicycle forward from rest on a level (horizontal) road?

(A) The pavement exerts a forward frictional force on the bottom of the rear wheel.

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.

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.

Walking on ice can be treacherous. In general, you are less likely to slip and fall if you lower your foot vertically into place on the ice as you take each step than you are if you slide your foot horizontally into place on the ice as you take each step. Why is the vertical landing method of walking on ice usually safer than the horizontal sliding method?

(A) The static frictional forces you can obtain from the ice using the vertical landing method are larger, and more effective at preventing sideways slips, than the sliding friction forces you are likely to obtain from the ice using the horizontal sliding method.

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

As a ball bounces on the floor, the floor exerts an upward support force on the ball. Can the amount of that upward support force on the ball be different from the ball's weight?

(A) Yes. It can be greater than the ball's weight and it can be less than the ball's weight.

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

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

(A) a constant downward force, both as it rises and as it descends.

A squirrel completes an amazing leap between two trees. While the squirrel was not touching anything and neglecting any effects due to the air, one aspect of the squirrel's motion that must remain constant was its

(A) angular momentum.

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

(A) considerably more than 10 meters above the ground.

You've learned to juggle 4 balls at once here on Earth. During a visit to the moon, where the acceleration due to gravity is about 1/6th its Earth value, you decide to try juggling those same 4 balls. You find that, on the moon, each ball has

(A) less weight and falls more slowly than on Earth. It undergoes the same acceleration as on Earth when exposed to the same force as on Earth.

A heavy container of orange juice sits on the shelf of your refrigerator's door. That orange juice

(A) makes it harder to change the door's angular velocity.

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

You are watching a baseball game and the pitcher has just thrown the ball toward the batter at home plate. Once the ball has left the pitcher's hand and is heading forward toward home plate, it experiences [neglect any effects due to the air]

(A) no horizontal force in the forward direction.

A helicopter is carrying you from the base of a mountain to a resort on the mountaintop. The helicopter is traveling along a straight-line path at a steady speed. The force that the helicopter exerts on you points

(A) upward (vertically)

Alice and Bob are carrying 50 pound bags of seeds from the sidewalk to your penthouse garden, 100 feet above the sidewalk. Alice carries bags up the stairs. Bob carries bags up a vertical ladder. Compare the work each person does on a bag while moving it from the sidewalk to the garden. [Neglect friction and air resistance, and assume that bags are motionless at the start and finish.]

(B) Alice and Bob do the same work on a bag.

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, but they push harder while moving downward than while moving upward. When during this exercise are you transferring energy to the step machine?

(B) As the pedals move downward.

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

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

You are riding a cable car from a valley to a mountaintop and are traveling straight toward the mountaintop at a steady pace. In which direction is the cable car pushing you?

(B) Directly upward.

A meteor is streaking toward city hall and will hit the building in a few second. As it moves through the sky, what physical quantities is the meteor carrying with it? [Ignore any effects due to air or Earth's gravity]

(B) Energy, momentum directed toward city hall, but no force.

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?

(B) Neither. They did equal amounts of work on their backpacks.

You are dragging a large couch across the floor in a straight line at a steady speed. Which of the following statements about the forces acting on the couch is correct?

(B) The amount of force that you're exerting on the couch must be equal to the amount of force that friction is exerting on it.

When an archer sends an arrow toward a target, the archer must aim the arrow above the target's bullseye (its center) in order for the arrow to hit that bullseye. If the archer uses a stronger bow and therefore a faster-moving arrow, how will that change how the archer aims the arrow in order to hit the same target's bullseye?

(B) The archer must still aim above the target's bullseye, but less far above the bullseye than with the slower-moving arrow

Which force is your weight? [The force that is your weight and not a force that is equal to your weight.]

(B) The force that causes you to accelerate downward when you are high above the surface of a trampoline

You are sitting in the lobby of a hotel, watching 4 people who are wearing backpacks. Which person is doing work on their backpack?

(B) The person who is riding upward at constant velocity in a glass elevator.

A tall luxury hotel has a rotating restaurant at its top. The disk-shaped floor of the restaurant rotates slowly about the center of the restaurant and completes one full rotation every 30 minutes. When the restaurant opens each day, the manager turns on the motors that make the restaurant spin, but it takes several minutes for the restaurant to begin spinning at its full angular velocity. Why doesn't the restaurant reach full speed immediately?

(B) The restaurant has a large rotational mass that resists rapid angular accelerations.

You are riding on a large carousel at an amusement park and are enjoying the moving scenery as the carousel spins about its center of rotation. The ride comes to an end and the carousel gradually slows to a stop. Why does it take so long for the carousel to stop rotating?

(B) The spinning carousel carries a large amount of angular momentum and the angular impulse needed to remove that angular momentum with a reasonable torque requires a long time.

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?

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

When you drive a car on a level (horizontal) road that is slippery with ice, you usually have no problems except when you try to speed up, slow down, or turn. Why does the icy road make those three actions hazardous? [neglect any effects due to air]

(B) Those three actions require the icy roads to exert frictional forces on the car's wheels.

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)?

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

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?

(B) While it is moving away from you.

A boy is bicycling up a hill and appears to need some help. As he passes you, you reach out with your hand and exert an uphill force of 10 N on him. When you do this, the boy exerts

(B) a downhill force of 10 N on you, because forces always come in equal but oppositely directed pairs

You're having trouble loosening a rusty bolt with a small wrench, so you borrow a large wrench from your neighbor. Exerting only a modest force on the handle of this new wrench easily unscrews the bolt. The large wrench helps because it

(B) allows you to exert your force far from the center of rotation, so that you produce a large torque on the bolt.

A Frisbee-catching dog leaps high into the air to capture a passing Frisbee. During the time that the dog is not touching the ground and neglecting any effects due to the air, the one aspect of the dog's motion that is constant is the dog's

(B) angular momentum.

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

(B) directly upward.

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

(B) is greater than, less than, or equal to the water bottle's weight, depending on the situation.

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?

(B) momentum

A racquetball court has rigid, immovable walls. You hit the rubber ball forward, toward the front wall of the court, and the ball bounces back at you. Before hitting the wall, the ball carried both energy and forward momentum. During its bounce, the ball transferred to the wall

(B) no energy and more forward momentum than it had before the bounce.

You throw your running shoes into the closest, but they bounce off the concrete wall and return to the middle of your rug. During their bounce, the shoes

(B) retained essentially all of their energy but transferred large amounts of momentum to the wall.

When you bounce a tennis ball off a concrete wall, the ball

(B) retains essentially all of its energy but transfers a large amount of momentum to the wall.

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

(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.

You are water-skiing behind your new yacht and the rope from the yacht is pulling you forward. At this moment, you are traveling in a straight line path at a constant speed. The net force you are experiencing is

(B) zero.

You are walking at constant velocity on a sidewalk that slopes gently uphill. What force(s) is the sidewalk exerting on you?

(C) A frictional force directed uphill, parallel to the sidewalk's surface, and a support force directed perpendicular to the sidewalk's surface.

You are pulling a toy wagon up a ramp that rises vertically 1 meter for every 8 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]

(C) It will accelerate downhill at 1/8th the acceleration due to gravity.

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.]

(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

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?

(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.

You are in an ordinary room (both its floor and ceiling are horizontal). You throw a ball directly upward and it bounces off the ceiling. While the ball is touching the ceiling, in which direction is the ceiling's support force on the ball?

(C) The ceiling's support force on the ball is directed downward.

You just dried your laundry and one of your socks is partly inside-out. You hold one end of the sock and jerk that end suddenly away from the rest of the sock. The sock immediately opens up to full length. What caused the sock to open up to full length?

(C) The sock's inertia.

A toy top is a disk-shaped object with a sharp point and a thin stem projecting from its bottom and top, respectively. When you twist the stem hard, the top begins to spin rapidly. When you then set the top's point on the ground and let go of it, it continues to spin about a vertical axis for a very long time. What keeps the top spinning?

(C) The top has rotational inertia.

You are bicycling along a quiet street when a child runs in front of you to retrieve a toy. You slam on the brakes and lock your wheels. The bicycle skids to a stop. What has become of your kinetic energy?

(D) It's now thermal energy in the wheels and ground

In a tower construction crane, a huge metal beam sits atop a vertical metal tower. The beam extends outward from the tower in two directions and it pivots about the top of the tower. A lifting cable hangs from one end of the beam and heavy weights hang from the other end of the beam. Since the lifting cable end of the beam is the only end that seems to do anything, what useful purpose does the weight-end of the beam serve?

(C) The weight-end of the beam ensures that the beam is approximately balanced about its pivot and experiences approximately zero torque due to gravity

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.

(C) Those two torques are equal in amount but opposite in direction.

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?

(C) You are doing zero work on each box.

Two children are balanced on a seesaw, but one child weighs twice as much as the other child. The heavier child is sitting half as far from the pivot as is the lighter child. Since the seesaw is balanced, the heavier child is exerting on the seesaw

(C) a torque that is equal in amount but oppositely directed to the torque the lighter child is exerting.

A rigid two-blade wind turbine that is experiencing zero net torque

(C) has a constant angular velocity.

You are standing on a cliff at the edge of a lake and dropping pebbles into the water. Each pebble takes 2 seconds to reach the water. After it has fallen for only 1 second, one of these pebbles is located

(C) much closer to you than to the water

You are cleaning up litter on the beach and have just thrown an empty bottle toward the recycling bin. Neglecting any effects due to the air, the net force on the bottle when it is midway between you and the recycling bin

(C) points straight down.

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

(C) points straight down.

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

(C) retains essentially all of its energy but transfers a large amount of momentum to the plate.

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

(C) the child who jumped forward reaches the water before the child who jumped upward.

A helicopter is hovering motionless above a disabled boat, while rescue workers use a rope to lift an injured sailor. While that sailor is being lifted upward, the net force on the motionless helicopter is

(C) zero.

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

(D) 50 newtons on your hand.

Which of the following is experiencing zero net force?

(D) A water-skier who is being pulled forward by a speedboat and is moving in a straight-line path at a steady speed.

A diver stands upright at the edge of the 10 meter platform at the Olympics. She jumps off the platform, folds into a ball shape, completes 3.5 somersaults, unfolds, and plunges head-first into the water. While she is not touching anything, which of the following physical quantities is constant? [Neglect any effects due to the air.]

(D) Her angular momentum.

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?

(D) Inertia.

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?

(D) It traveled 1/4 of the distance to the ground.

You toss a basketball straight up. Disregarding any effects of due to the air, what force or forces are acting on the basketball while it is above your hands?

(D) Its weight.

You are arm-wrestling another friend and find that you are almost perfectly matched. Your pair of arms is vertical and motionless, even though you are both trying hard to win. To begin winning, you want that pair of arms to rotate counterclockwise from your perspective. What must you do to make that happen?

(D) The counterclockwise torque you exert on the pair of arms must be greater in amount than the clockwise torque your friend is exerting on that pair.

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?

(D) Upward

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]

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

You are moving two wagons on level ground. One wagon has a mass of 100 kilograms and the other has a mass of 200 kilograms. Neglect friction and air resistance. When you push equally hard on each wagon, the 100 kilogram wagon

(D) accelerates twice as quickly as the 200 kilogram wagon.

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

(D) angular momentum

A cheerleader leaps into the air with her arms and legs extended and then pulls herself into a compact ball to complete a somersault. She opens up again and lands on her feet. During the time that she is not touching the ground, one aspect of her motion that is constant is her

(D) angular momentum.

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

(D) as you push them away from you and as you pull them toward you.

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

(D) at approximately the same time and at the same distance from the table.

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

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

A rigid two-blade wind turbine that is experiencing zero net torque

(D) has a constant angular velocity.

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

(D) is constant but her rotational mass decreases.

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

(D) is zero

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

(D) it barely moves downward as you push downward on it, so you do almost zero work on it.

Your favorite marble rolls off the deck and falls for 2 seconds before hitting the ground. After only 1 second of falling, the marble was

(D) much closer to the deck than to the ground.

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

(D) no horizontal force in the forward direction.

You are watching a tennis match and the server has just hit the ball toward her opponent on the other side of the court. Neglect any effects due to the air. Once the tennis ball has left the server's tennis racket and is traveling forward, the ball experiences

(D) no horizontal force in the forward direction.

Your car skids off the road in bad weather and crashes into a tree. Fortunately, the airbag inflates and protects your head from injury. By coming to a stop in the airbag instead of on the steering wheel, your head transfers

(D) the same amount of momentum to the car but over a longer period of time and with a smaller force.

While wandering in the dark toward the refrigerator, you accidentally walk into a concrete wall and come to a sudden stop without bouncing back. Fortunately, that wall was covered with a soft fabric wall hanging. Coming to a stop on the soft fabric was more pleasant than coming to a stop on the concrete because you transfer

(D) the same momentum to either surface, but you transfer it more slowly to the fabric than to the concrete.

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

(D) the team on the right

You toss your cellphone directly upward and watch it rise to its peak height. At the moment that it reaches that peak height, its velocity is

(D) zero and its acceleration is downward.

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.

A downhill skier is descending a snow-covered mountain. The skier steps off of a level region of the mountain and onto a steep slope. The skier begins to accelerate rapidly downhill on the slope. What force is causing the skier to accelerate downhill?

A) The downhill ramp force that is the sum of the skier's weight and the support force exerted on the skier by the snow-covered slope.

You are talking on your cellphone and you accidentally ride your bicycle off the road. You realize that you are going to collide with either a tree or a garbage can, so you must choose which object to hit. The tree will not move at all if you hit the tree, but the garbage can will move if you hit the garbage can. How will your choice of object affect the energy you transfer to that object when you hit it? [Fortunately, you are going slowly, so you won't be injured regardless of your choice.]

B) You will transfer energy if you hit the garbage can, but you will not transfer energy if you hit the tree.