4. From a stopped position, a car starts to accelerate
at 3 m/sec2. Which graph below best represents the
motion of the car?
1.
A. Z
B. Y
What is the magnitude (size) and direction of the
cumulative force acting on the car shown in the
picture above?
A. 30 N to the left
B. 2500 N up
C. 30 N to the right
D. 2500 N down
2. A truck pulls a trailer from a standstill with a
constant force. After 2 minutes, the truck is moving
at 48 km/hr. If the same truck applies the same
constant force to pull a second trailer which is 3
times the mass of the first trailer, how fast will the
truck be moving after 2 minutes?
A. 8 km/hr
B. 64 km/hr
C. X
D. W
5. Two teams are playing tug-of-war. Each team is
pulling on the rope with a force of 500 newtons. A
ribbon is tied to the middle of the rope to determine
the winner. Which of the following would result in
the greatest acceleration of the ribbon?
A. A player on Team B who was pulling with a
force of 150 newtons leaves the game.
B. A player added to Team A pulls on the rope
with a force of 130 newtons.
C. A player added to Team A pulls with a force
of 250 newtons and a player added to Team B
pulls with a force of 250 newtons.
D. A player added to Team B pulls on the rope
with a force of 120 newtons.
C. 16 km/hr
D. 48 km/hr
3. Ming drew the vector diagram below to represent
the motion of a car in front of her house.
6. Which of the following determine an object's
velocity?
A. speed and mass
B. speed, direction, and acceleration
C. speed and direction
D. direction and acceleration
Based on the diagram, which of the following is
true?
A. The car is backing up.
B. The car is slowing down.
C. The car is far away.
D. The car is accelerating.
7. A cart is rolling across the floor at a constant
velocity of 2 m/s to the right. The cart is pushed
again to the right, and it starts to accelerate.
How are the force of the push and acceleration of
the cart related?
10. Which of the following is a unit of acceleration?
A. kg-m/sec2
B. m/sec
C. m/sec2
D. kg-m/sec
A. The unbalanced push causes the cart to
accelerate.
B. The force of gravity makes the car accelerate.
C. The force and acceleration are not related.
D. The balanced push causes the cart to
accelerate.
11. Penny has two dogs: Fluffy (left) and Butch
(right). Penny thinks her dogs might enjoy a little
adventure. She owns two identical small red wagons
with four wheels.
8. Neil Armstrong weighed more on Earth than he
did on the moon because the Earth has a greater
A. electromagnetic field.
B. gravitational force.
C. density.
Fluffy
D. atmosphere.
9. Which of the following best describes the
difference between speed and acceleration?
A. Acceleration is the distance an object travels
within a specific unit of time, whereas speed is
the rate at which the acceleration or direction of
an object is changing.
B. Speed is the distance an object travels within a
specific unit of time, whereas acceleration is the
rate at which the speed or direction of an object
is changing.
C. Acceleration is the distance an object travels
within a specific unit of time, whereas speed is a
measure of the force necessary to change the
acceleration of an object.
D. Speed is the distance an object travels within
a specific unit of time, whereas acceleration is a
measure of the force necessary to change the
speed of an object.
Butch
Penny puts Fluffy in one wagon and pushes the
wagon, once, as hard as she can. Penny puts Butch
in the other wagon and pushes it once, also as hard
as she can. Both of the wagons travel across a level
surface. Will the motion of the two wagons be
different?
A. Yes; Butch's wagon will move faster.
B. Yes; Fluffy's wagon will stop first.
C. Yes; Fluffy's wagon will move faster.
D. No; the wagons will both move in the same
way.
12. A car is traveling south at a speed of 63 miles
per hour and then begins traveling west but
continues traveling at the same speed. Which of the
following has changed?
A. velocity
B. mass
C. gravity
D. speed
13. Mike and Joe take turns pitching a baseball, and
Drew catches it. Mike can throw the ball harder
than Joe can.
16. The position vs. time graph below shows the
motion of Mr. Diaz's car.
Which of the following statements is true?
A. The ball is heavier when Mike throws it.
B. The ball requires more force to stop when Joe
throws it.
C. The ball travels faster when Mike throws it.
D. The ball hits Drew's glove harder when Joe
throws it.
Based on the graph, which of the following is true?
A. The car's speed is constant.
B. The car is slowing down.
C. The car is driving up a hill.
D. The car is accelerating.
14. The measure of an object's speed and direction
is the object's ______.
17. If the forces acting on an object are balanced,
the object is
A. velocity
A. accelerating or decelerating.
B. acceleration
B. accelerating or in constant motion.
C. speed
C. at rest or in constant motion.
D. momentum
D. at rest or accelerating.
15. An object's motion changes
A. only if the object is at rest when a force acts
upon it.
18. In a football game, a defensive lineman exerts a
force upon an offensive lineman, causing the
offensive lineman to be accelerated backward at 2
m/s2. If the offensive lineman's mass were doubled,
how much force would the defensive lineman have
to apply to accelerate the offensive lineman 2 m/s2
backward?
A. twice as much
B. when the forces acting on the object remain
balanced.
C. only when a nonzero net force is applied to
the object.
D. all of these
B. the same amount
C. four times as much
D. half as much
19. Suppose a bicycle was coasting on a level
surface, and there was no friction. What would
happen to the bicycle's speed?
A. The speed would increase since there is no
friction.
B. The speed would remain constant.
23. Ashley made a paper airplane. When she threw
the airplane in the house, it always flew straight
where she aimed. Now she wants to throw the plane
to her pet dog, Scruffy, who is in the backyard.
There is a steady wind blowing East.
C. The speed would decrease but you would
never stop.
D. The speed would decrease until you finally
came to a stop.
20. Sandy puts a paper clip on the table. Then, she
puts a magnet near the paperclip. The paperclip
begins to move.
The paperclip has _______ forces acting on it.
A. only gravitational
B. unbalanced
C. balanced
D. only magnetic
21. A book is sitting on a table, completely still.
What would happen if gravity suddenly stopped
affecting the book?
A. The book would stay where it is.
B. The book would fall.
C. The book would move upward.
D. The book would move sideways.
22. Lydia is running on the sidewalk by her house.
She is running at a speed of 3 meters per second.
Over a period of 10 seconds she increases her speed
to 5 meters per second. Lydia's
average _______ over this 10 second period is
0.2 m/s2.
A. position
B. force
C. acceleration
D. speed
A diagram of Ashley's backyard is shown above. If
she aims her throw directly at Scruffy, where is the
paper airplane most likely to end up?
A. in the pool
B. at the tree
C. on the patio
D. at Scruffy
Answers
1. C
2. C
3. C
4. D
5. D
6. A
7. C
8. B
9. A
10. B
11. B
12. C
13. C
14. B
15. A
16. C
17. A
18. A
19. D
20. D
21. A
22. C
23. D
24. C
25. A
26. B
27. B
28. A
29. C
30. A
Explanations
1. The weight of the car, 2500 N, is pushing down while the road is pushing up with a
force of equal magnitude. Those forces cancel each other out. The car is being pushed to
the left with a force of 20 N and to the right with a force of 50 N. Thus, the cumulative
force is 30 N to the right.
2. The gravitational force on the ball is consistent throughout the ball's flight. On the way
up, the ball goes from 20 m/sec to 0 m/sec. On the way down, the ball goes from 0 m/sec
to 20 m/sec.
3. To solve this problem, you need to divide the speed of the truck (with one trailer
attached) by 3 because the second trailer is 3 times the mass of the first trailer.
4. A vector diagram can be used to tell how quickly something is moving. If the arrows
are the same length, the speed is constant. If the arrows are shorter than the previous
arrow, the speed is decreasing. The arrows in Ming’s diagram are longer than the
previous arrows, so the car she saw is accelerating.
5. When a car accelerates, the speed is NOT constant (so the answer is not graph X). It
starts off slowly and accelerates at a rapid pace. During acceleration, increasing distance
is covered in a shorter amount of time (usually seconds).
6. The game starts with each team pulling with a force of 500 newtons. So, the net force
on the ribbon is zero: 500 - 500 = 0.
The greater the net force on the ribbon, the greater the acceleration of the ribbon. So,
calculate the net force for each situation.
If each team adds a player pulling with a force of 250 newtons, then each team would be
pulling with a force of 750 newtons: 500 + 250 = 750. Since both teams are still pulling
with an equal force, the net force on the ribbon is still zero (750 - 750 = 0).
If a player added to Team B pulls with a force of 120 newtons, the ribbon would
experience a net force of 120 newtons in Team B's direction.
If a player added to Team A pulls with a force of 130 newtons, the ribbon would
experience a net force of 130 newtons in Team A's direction.
If a player on Team B who was pulling with a force of 150 newtons leaves the game, then
Team B will pulling with a force of 350 newtons, compared to Team A's 500 newtons.
The ribbon would experience a net force of 150 newtons in Team A's direction.
Therefore, this scenario will result in the greatest acceleration of the ribbon.
7. Velocity is a vector quantity. This means that an object's velocity is determined by not
only its speed but also its direction.
8. The bikes on the ticker tape diagram represent the motion of Jordan and his bike. A
large distance between the bikes would mean he was moving quickly. A small distance
means would mean he was moving slowly. An increasing distance between the bikes
would mean Jordan was accelerating. The bikes on the tape are an equal distance apart.
This means he was moving at a constant speed.
9. The application of an unbalanced force (the push) causes the cart to accelerate.
When the cart is in constant motion, the forces are balanced and there is no acceleration.
Once an unbalanced force is added, the cart's speed changes.
10. Earth has a gravitational acceleration of 9.8 m/sec2 and the moon has a gravitational
acceleration of 1.63 m/sec2. Because the gravitational pull on the Earth is more than that
on the moon, he will weigh more on Earth than he did on the moon.
11. Speed is the distance an object travels within a specific unit of time. The average
speed of an object can be calculated by dividing distance over time. Acceleration, on the
other hand, is the rate at which the speed or direction of an object is changing.
Acceleration can be positive or negative.
12. Acceleration is measured by dividing the distance traveled by a unit of time squared;
therefore, m/sec2 is a unit of acceleration.
13. If Penny pushes both wagons with an equal force, Fluffy's wagon will move faster
because an object with less mass can speed up more easily. Since Fluffy is less massive
than Butch, the same push will make her move more quickly.
14. Inertia is a property of matter that is related to its mass, regardless of its motion. An
object with a small mass has less inertia than an object with a large mass.
Ball Z has the largest mass. Therefore, it has the most inertia.
15. Velocity is a vector quantity. This means that an object's velocity is determined by
not only its speed but also its direction. Therefore, if the direction the car is moving
changes, then so does its velocity.
16. Mike throws the ball harder, with a greater force, so the ball travels faster when
Mike throws it than when Joe does.
17. Objects that are moving do not stop moving on their own. Something must act on an
object to make it stop moving. So an object will keep moving until a force pushes or
pulls it to a stop.
18. Velocity is a vector quantity. This means that an object's velocity is determined by
not only its speed but also its direction.
19. The trains on the ticker tape diagram represent the motion of the train. A large
distance between the trains means the train was moving quickly. A small distance means
it was moving slowly. An equal distance between the trains means it was moving at a
constant speed. An increasing distance between the trains means the train was
accelerating.
20. If the forces of friction are ignored, all objects fall at the same rate; therefore, Ball A
and Ball B would hit the ground at the same time.
21. Every action has an equal and opposite reaction; therefore, when the person's feet
push backward on the sidewalk, and the sidewalk pushes forward on the person, thereby
propelling the person forward down the street.
22. A net force is the sum of the unbalanced forces acting on an object. An object's
motion changes only when a nonzero net force is applied to the object. When a net
force is applied to an object, the object's speed and/or direction changes.
If the forces acting on the object are balanced, they will cancel each other out and will not
cause the motion of the object to change.
23. If a position vs. time graph shows a sloped, straight line, then it represents an object
moving at constant speed. If the slope of the line is changing, then it represents an object
with a changing speed.
In this case, the slope of the line is changing. It is increasing with time. So, the rate at
which Mr. Diaz's car is moving is also changing. Mr. Diaz's car is accelerating.
24. If the forces acting on an object are balanced, that means that the forces are equal, so
the object is at rest or in constant motion.
If the object is accelerating or decelerating, a force is acting on the object to slow it down
or speed it up, so that force makes it unbalanced.
25. The magnitude, or amount, of an object's acceleration is directly proportional to the
magnitude of the force exerted upon it and inversely proportional to its own mass.
In this case, if the offensive lineman's mass were doubled, then the force exerted upon
him would also have to be doubled to produce the same acceleration (2 m/s2).
26. The speed would remain constant due to inertia because objects in motion stay in
motion unless they are disturbed by an external force.
27. The paperclip has unbalanced forces acting on it.
The paperclip has a magnetic force, a gravitational force, and a force from the table
acting on it.
28. An unmoving object will remain motionless unless an unbalanced force pushes or
pulls on it. When gravity is acting on the book, it is being pulled down. But at the same
time, the table is balancing this force by pushing up. If gravity suddenly vanishes, both of
these forces will disappear. With zero forces acting on the book, it will stay where it is.
29. Acceleration is the rate at which the speed or direction of an object is changing.
Average acceleration can be calculated by dividing the change in the speed of an object
by the time over which the change occurs. Lydia's change in speed is 2 m/s and the
change occurs over a time period of 20 seconds. Therefore, her acceleration can be
calculated by:
2 m/s ÷ 10 s = 0.2 m/s2.
30. An object's motion is the result of the combined effect of the forces acting upon the
object.
Ashley's throw will apply a force on the plane in the direction of Scruffy (north). The
wind will also apply a force on the plane, in the east direction.
So, the combined effect of the forces acting upon the airplane will be a force in the
northeast direction. This will most likely direct the plane to the pool.