Deck 1: The Laws of Motion, Part 1

Question 1

Suppose you have two cars, and the larger one is twice as massive as the smaller one. If you and a friend push on them so that their accelerations are equal, how must the forces applied to the cars compare?

A) The force on the larger car is equal to that on the smaller car
B) The force on the larger car is ½ that on the smaller car.
C) The force on the larger car is twice that on the smaller car.
D) The force on the larger car is more than three times that on the smaller car.

Answer 1

The force on the larger car is twice that on the smaller car.

Question 2

Which of the following devices on a car can be used to cause the car to accelerate?

A) The gas pedal
B) The brake pedal
C) The steering wheel
D) All the above

Answer 2

All the above

Question 3

The acceleration of an object is equal to

A) the rate of change of its position
B) the rate of change of its velocity
C) the rate of change of its speed only
D) the time an object has been in motion

Answer 3

the rate of change of its velocity

Question 4

Suppose you are at a stop light and realize that an important antique physics textbook sale ends in five minutes. Naturally, you start off very rapidly. To you, some papers on the dashboard fly straight backwards. To an observer on the ground they

A) remained where they were.
B) moved forward rapidly.
C) moved backwards rapidly.
D) fell straight down.

Question 5

The SI units of acceleration are

A) m/s
B) kgm/s²
C) m/s²
D) kg m²/s²

Question 6

Suppose you have a car traveling down the road at constant speed and not changing direction. It is experiencing gravity, wind resistance and frictional forces from the road. What can be said about the car's acceleration?

A) It is accelerating because there are forces acting on it.
B) It accelerating because the motor is running, propelling the car forward.
C) It is not accelerating because gravity holds it down.
D) It is not accelerating because it has constant velocity.

Question 7

Suppose you are driving north and suddenly hit your brakes to avoid a dog in the road. As you come to a stop your acceleration is directed

A) North
B) South
C) Nowhere because acceleration is a scalar
D) Downwards

Question 8

If you are backing up but slowing down, your acceleration is directed

A) backwards
B) nowhere
C) forwards
D) to the left

Question 9

Under what conditions are the values of average speed and the magnitude of the average velocity equal?

A) When moving in a straight line
B) When moving in a straight line and not turning around
C) When moving in a circular path
D) When walking around the perimeter of a rectangle

Question 10

You are making a round trip from City A to City B and back to City A again at constant speed. At what point in the trip is your average speed equal to three times the magnitude of your average velocity?

Question 11

A frequent flyer is suing an airline. She claims that during landing, the plane's rapid acceleration caused a suitcase on a luggage rack in front of her to fly backwards and hit her. Using any of Newton's laws of motion, please support or refute the passenger's claim.

Question 12

A friend states Newton's First Law of Motion as "An object will move in a straight line unless acted upon by a force" Please evaluate the scientific merit of his statement.

Question 13

You walk in a given direction for 20 m during the first 5 seconds of a trip and then 15 m during the next 2 seconds. Your average speed is equal to

A) 8 m/s
B) 2 m/s
C) 5 m/s
D) -5 m/s

Question 14

To cause a 25 kg object to experience an acceleration of 2 m/s² the net force that needs to be applied to the object is

A) 10 N
B) 5 N
C) 50 N
D) 100 N

Question 15

A net force of 8 N is applied to a 2 kg object. The object's acceleration is

A) 4 m/s²
B) 8 m/s²
C) 16 m/s²
D) 2 m/s²

Question 16

An object experiences a net force of 20 N and has an acceleration of 4 m/s². The object's mass must be

A) 20 kg
B) 5 kg
C) 80 kg
D) 2 kg

Question 17

At a speed of 12 m/sec how far can you travel in one minute?

A) 12 m
B) 72 m
C) 60 m
D) 720 m

Question 18

Consider a 6 kg box of holiday candy on a horizontal surface such as a table. There is a 10N applied force to the right and a 7 N frictional force to the left. Suppose the block moves 3 m to the right across the table, to its impending doom of hungry guests.
-Please calculate the work done by the 10 N force.

Question 19

Consider a 6 kg box of holiday candy on a horizontal surface such as a table. There is a 10N applied force to the right and a 7 N frictional force to the left. Suppose the block moves 3 m to the right across the table, to its impending doom of hungry guests.
-What is the work done by the 7 N frictional force?

Question 20

Is it possible for the magnitude of an object's average velocity to be greater than its average speed? How about average speed being greater than the magnitude of the average velocity? Please explain.

Question 21

Suppose an ice skater is moving on the surface of a frozen lake at constant velocity. What is true about the external (outside) forces acting on the skater?

A) There are none.
B) There could be some but they all cancel out.
C) Gravity can be ignored.
D) The all are perfectly horizontal.

Question 22

The value of the average velocity for any round trip is equal to

A) Total distance traveled divided by total trip time.
B) The final acceleration multiplied by trip time
C) Zero.
D) The person's speed halfway through the path.

Question 23

Suppose that the night before your big physics exam you stayed up late watching stand - up physics comedians. Sides sore from having laughed too hard you come to class and are in the middle of the test when you get stuck. You are doing a calculation problem and know the answer must have units of velocity and are searching for a possible formula. Which of the following formulae would work for the problem?

A) acceleration x time
B) acceleration / time
C) velocity squared x distance
D) mass / volume

Question 24

The neighborhood joker comes up to you and is really on a roll this morning. After several "good ones" they then say "OK so you're taking physics, right? Here's one - if the acceleration of gravity is 9.8 m/s² then why isn't everything accelerating? HAHAHA". Being a dedicated student you give this question some real thought and come up with a reasonable response. You might say

A) All things really do accelerate but we accelerate with them so we can't tell.
B) Gravity acts only on things that are not touching a surface.
C) Gravity is just part of the story and it is the total net external force that determines acceleration.
D) Most objects have too much inertia for us to see them accelerate under the influence of gravity.

Question 25

You are in your car at a stop light and start off really quickly. As you accelerate several items fall off the dashboard and on to the floor. Please explain why your car is a non - inertial reference frame.

Question 26

A friend is casually talking with you about physics concepts and brings up the following claim. They say that average speed for a trip is total distance divided by total time, which is true. Then they say that if the trip consists of a person traveling at two different speeds for two different times then you can get the average speed by just finding the average speeds for the two parts of the trip and then take their average. Is their claim true? Please explain.

Question 27

Your class is rather unhappy with the instructor, and they pitch in and decide to fund a sabbatical for him to go to Mars. Unbeknownst to the students the following semester, the instructor has made long distance course arrangements so the "show can go on". The instructor begins talking about mass, weight and related things. He correctly makes which following statement:

A) his mass is still essentially unchanged but his weight is less than on earth.
B) his weight is still essentially unchanged but his mass is less than on earth.
C) neither his weight nor his mass have changed much.
D) his weight and mass have both changed significantly.

Question 28

Suppose you are a football player and you kick a ball for a field goal. Ignoring air resistance, the ball's horizontal velocity

A) changes throughout the path due to gravitational acceleration
B) is zero at the top of the path
C) is maximum at the top of the path
D) remains constant throughout the path

Question 29

A child throws a ball perfectly horizontally at the same time a dirt clod falls off it at the same height above the ground. The clod falls vertically downward. Ignoring air resistance, the time when the clod hits the ground will

A) be equal to the time the ball hits the ground
B) be earlier than when the ball hits
C) be later than when the ball hits
D) not depend upon how high it started falling from

Question 30

Your weight and mass are different in that

A) your weight is measured in kg but not your mass
B) your mass depends upon local gravity but your weight does not.
C) your weight depends upon local gravity but your mass does not.
D) being weightless means that you have to lose mass.

Question 31

Suppose a tree branch falls down to the ground with constant acceleration and takes 2 seconds to hit the ground. Which of the following statements regarding the path of the branch is true?

A) It covers the same distance during the first second as it does during the last second.
B) It covers more distance during the last second.
C) It covers less distance during the last second.
D) Its acceleration is increasing during the time it falls

Question 32

Suppose you go from the earth to a planet where the acceleration of gravity is 2.5 m/s². On the new planet your weight will be about

A) be ¼ its value on Earth
B) quadruple
C) double
D) the sane as

Question 33

Suppose you go from the earth to a planet where the acceleration of gravity is 3 m/s². On the new planet your mass will

A) be 1/3 its value on Earth
B) be 9 times its value on Earth
C) be 3/10 its value on Earth
D) not change

Question 34

A projectile is thrown directly upward and caught again. At the top of its path

A) it stops accelerating
B) its vertical velocity is zero
C) its horizontal velocity changes
D) its acceleration changes

Question 35

Suppose you throw a ball downwards with a certain initial speed from a certain height h above the ground, and someone else throws a ball directly upward at the same speed, so the two balls collide. Will the two balls collide in the middle of the path (h/2), above the middle or below? Please explain.

Question 36

Suppose you are on another planet and you want to measure its acceleration of gravity so you drop an object from rest. It hits the ground, traveling a distance of 0.8 m in 0.5 second and then bounces back up and stops exactly where it started from.
-Please calculate the acceleration of gravity on this planet.

Question 37

Suppose you are on another planet and you want to measure its acceleration of gravity so you drop an object from rest. It hits the ground, traveling a distance of 0.8 m in 0.5 second and then bounces back up and stops exactly where it started from.
-Taking downward to be positive, how does the ball's average speed compare to the magnitude of its average velocity on the way down?

Question 38

Suppose you are on another planet and you want to measure its acceleration of gravity so you drop an object from rest. It hits the ground, traveling a distance of 0.8 m in 0.5 second and then bounces back up and stops exactly where it started from.
-Taking the beginning of the motion as the time the ball was dropped, how does its average speed compare to the magnitude of its average velocity on the way up?

Question 39

Suppose you are on another planet and you want to measure its acceleration of gravity so you drop an object from rest. It hits the ground, traveling a distance of 0.8 m in 0.5 second and then bounces back up and stops exactly where it started from.
-With what speed did the ball hit the ground?

Question 40

Suppose you are on another planet and you want to measure its acceleration of gravity so you drop an object from rest. It hits the ground, traveling a distance of 0.8 m in 0.5 second and then bounces back up and stops exactly where it started from.
-When distance is divided by time the result is 1.6 m/sec. Please explain why this result does not agree with the answer in (D).

Question 41

When someone throws a football, what should the launch angle be (ignoring air resistance) so that it travels a maximum distance?

Question 42

Suppose your instructor staggers into class after an all - night physics textbook sampling party and states Newton's second law as "If an object experiences a force then it will accelerate. If there are no forces acting on it then it will stand still." Please give three examples (from class, real life or made up) which expose mistakes on his part and briefly explain how they show his inaccuracies.

Question 43

You throw brick straight up. Ignoring air resistance, after it leaves your hand it will experience

A) only the downward force of its weight, both before and after it reaches its maximum height.
B) both an upward force, and the downward force of its weight after it rises. The upward force will gradually diminish to zero at the ball's maximum height, after which the ball will experience only the
Downward force of its weight.
C) an upward force as it rises. This upward force will gradually diminish to zero at the ball's maximum height, after which the ball will experience only the downward force of its weight.
D) the upward force of its weight as it rises. Once the ball reaches its maximum height, it will begin to experience the downward force of its weight.

Question 44

If you have a mass of 80 kg and are in a planet where the acceleration of gravity is 5 m/s², your weight on the planet is

A) 400 N
B) 4000 N
C) 16 N
D) 80 N

Question 45

A gymnast jumps upward with an initial speed of 10 m/s. She is in the air for a total time of

A) 1 second
B) 5 seconds
C) 2 seconds
D) 10 seconds

Question 46

The maximum height above the ground for a the gymnast jumping straight upward with an initial speed of 10 m/s is

A) 5 m
B) 10 m
C) 2 m
D) 15 m

Question 47

A car starts from rest and accelerates at 4 m/s². How much time will it take the car to reach a speed of 20 m/s?

A) 5 s
B) 10 s
C) 4 s
D) 8 s

Question 48

Suppose you are a football player and you kick a ball for a field goal. Including air resistance, the ball's horizontal velocity

A) changes throughout the path due to gravitational acceleration
B) is zero at the top of the path
C) decreases throughout the path
D) increases throughout the path

Question 49

Suppose an object is traveling at terminal velocity, so it is falling through air but not accelerating. How does the force of air resistance compare to its weight?

A) The two forces are equal and opposite.
B) The two forces are equal.
C) Air resistance is greater than the ball's weight.
D) Air resistance is less than the ball's weight.

Question 50

Suppose you drop an object out of the window of a building and wait for it to hit the ground. How does the halfway point in distance compare to the halfway point in time? Please explain.

Question 51

Suppose a 2 kg object is falling through the air and accelerating downwards at 8 m/s². Taking g = 10 m/s² What is the magnitude and direction of the force of air resistance on it?

A) 2N downward
B) 2N upward
C) 1N downward
D) 1N upward

Question 52

Suppose you throw a ball upwards with a certain initial speed from a certain height h above the ground, and you wait for it to go up, stop and come back down to the same (initial) position. Including air resistance, how will its speed hitting the ground on the way back down compare to its launch speed? Please explain.

Question 53

In our calculations of motion, we have ignored certain aspects of the object and its environment. Please briefly discuss three such aspects, and what kind of differences they make.

Question 54

Suppose you weigh 986 N. How much force does the Earth exert on you, if any?

A) it cannot be determined
B) 986 N
C) 98.6N
D) none

Question 55

You are riding a bicycle into a strong head wind, but manage to keep moving in a straight line at a constant speed. The net force on you is

A) 0
B) in the direction of your motion
C) in the direction tie wind is pushing you (backwards)
D) downward due to your weight

Question 56

In order to do a positive amount of work you must

A) exert a force and move in the direction of the force
B) exert a force and just move
C) exert a force or move
D) change an object's position

Question 57

Driving down the road, you hit an insect. How does the force your car exerts on the insect compare to the force the insect exerts on the car?

A) The force the car exerts on the insect is less.
B) The force the insect exerts on the car is less.
C) The two forces are equal in magnitude.
D) The insect exerts no force on the car

Question 58

Suppose your car is on a 5% grade, meaning that for every 100 m you travel along the road you raise or lower only 5 m in elevation. If your car weighs 1500 kg, what is the component of its weight parallel to the road?

A) 15000 N
B) 1500 N
C) 7500 N
D) 750 N

Question 59

Suppose you are helping take groceries inside your house and you carry a heavy bag from the car to the house, keeping the bag at a constant level and walking at a constant speed. During your trip the work you do on the bag is

A) positive
B) 0
C) negative
D) equal to its potential energy

Question 60

Suppose you push horizontally on the wall of a building. For you to do work on the wall, which of the following need to happen?

A) the wall moves away from you
B) the wall lifts up
C) the wall moves sideways
D) b and c

Question 61

Suppose Larissa throws a ball up in the air and it comes back down to the same place she threw it from. Ignoring times when the ball is in contact with her hand, and ignoring air resistance (friction with the air), identify the point(s) of
-Maximum and minimum potential energy.

Question 62

Suppose Larissa throws a ball up in the air and it comes back down to the same place she threw it from. Ignoring times when the ball is in contact with her hand, and ignoring air resistance (friction with the air), identify the point(s) of
-Maximum and minimum kinetic energy.

Question 63

Suppose Larissa throws a ball up in the air and it comes back down to the same place she threw it from. Ignoring times when the ball is in contact with her hand, and ignoring air resistance (friction with the air), identify the point(s) of
-Maximum and minimum total mechanical energy.

Question 64

Suppose Larissa throws a ball up in the air and it comes back down to the same place she threw it from. Ignoring times when the ball is in contact with her hand, and ignoring air resistance (friction with the air), identify the point(s) of
-Please briefly describe the energy transformation taking place as the ball rises in the air, and also when it is falling back to earth.

Question 65

Suppose you do some work on an object. Think of two ways you can tell work has been done on the object just by observing the object.

Question 66

You are riding on a flat train car and are climbing up the side of a hay stack. You are half way up the stack and are maintaining a steady height. You and the stack are moving steadily along the straight tracks at constant speed. The net force on you is

A) downhill-toward the bottom of the front of the stack.
B) zero.
C) uphill-behind you.
D) horizontal-parallel to the tracks.

Question 67

You push on a box with a horizontal force of 20 N and the box moves a distance of 8 m. The amount of work you have done on the box is

A) 160 J
B) 320 J
C) 20J
D) 0

Question 68

Suppose you do 1000 J of work on a 5 kg object, and all the work went into lifting it above the ground. How high above the ground will the object be when all the work has been done?

A) 100 m
B) 5 m
C) 20 m
D) 1 m

Question 69

What is the potential energy of a 40 kg box that is 6m above the ground?

A) 240 J
B) 2400 J
C) 6 J
D) 60 J

Question 70

Suppose you push a 50 kg box 10 m up a frictionless incline that has a 10% grade. What is the change in potential energy for the box?

A) 500 J
B) 5000 J
C) 250 J
D) 2500 J

Question 71

In order to do a negative amount of work you must

A) exert a force and move in the direction of the force
B) exert a force and move opposite to the direction of the force.
C) exert a force or move
D) change an object's position

Question 72

Please briefly discuss two situations where no work is done by a force.

Question 73

Suppose you use a ramp to lift a 200 kg object. You raise it 2 m above the ground and did 5000 J of work. Assuming that gravity and friction could be the only forces you had to work against, was there any friction, and if so how much work did you have to do against it?

Question 74

Your friend and you are at the mall shopping. She stops, grabs your arm and exclaims that she is worried about her physics test she took last Friday because she ignored the work done by (or against) the normal force when an object slides across a surface. What would you (correctly) reply to her?

Question 75

Your friend and you are at the mall shopping. She stops, grabs your arm and exclaims that she is worried about her physics test she took last Friday because she ignored the work done by (or against) the normal force when a person is being lifted in an elevator. What would you (correctly) reply to her?

Question 76

In physics we often make approximations. We say, for example that when you push against a stationary wall, no work is done. Thinking about details of the system is this true? Please explain.