Midterm Review: Physics Practice
Unit 1: Experiments, Dimensional Analysis, Right Triangle Analysis
1.) Define:
 Independent variable
 Dependent variable
 Control variables
 Control group
2.) Julie is conducting an experiment to see if eating an orange during lunch leads to higher vitamin C
levels in the blood. Julie has 300 friends participate in this study. She has 150 friends eat the school
lunch for a month. Another group of 150 eats the school lunch and an extra serving of vegetables for a
month. Every participant in the study eats the same thing for breakfast and dinner. Furthermore, no
participant is allowed to take vitamins. Julie measures the participants vitamin C levels at the beginning
of the month and at the end of the month. She then compares vitamin C levels across the groups to see
if eating more vegetables leads to higher vitamin C levels in the bloodstream.
 In this experiment, what was the independent variable used by Julie?
 In this experiment, what was the dependent variable used by Julie?
 What are two control variables used by Julie in this experiment?
3.) Bob wants to know if studying more hours for the physics midterm will result in higher midterm test
scores. He has 2 of his friends study for about two hours every day over the weekend. Bob also has 2
friends not study at all. All of his friends take the midterm. He compares the results of the 2 groups to
see if studying effects their test scores in physics.
 What is the independent variable in this sample experiment?
 What is the dependent variable in this sample experiment?
 What is the control group in this sample experiment?
 Please provide at least two improvements for Steve’s experiment:
4.) How many days is 172800 seconds?
5.) How many kilometers (km) are in 55,000 millimeters (mm)?
6.) If a fast turtle goes 1 kilometer (km) every hour (hr), what is his speed in m/s?
7.) Find the length of side x on the given triangle:
47 0
40m
x
Page 1 of 9
38m
Midterm Review: Physics Practice
8.) Find the length of side x in kilometers on the given triangle:
x
2,500m
Unit 1 Answers:
1.)
Independent variable –the variable you change in an experiment
Dependent variable – the variable that changes due to changing the independent variable
Control variables – variables that you hold constant to make sure they do not change the outcome of an
experiment
Control group – A group that you do not change that offers a comparison
2.)
Independent variable: eating an orange or not
Dependent variable: level of vitamin C
Two control variables: no vitamins & eats same breakfast and dinner.
3.)
Independent variable: how much each friend studies
Dependent variable: how well each friend does on the midterm
Control Group: the group that does not study
Two improvements: 1). Larger sample size 2). Repeated Trials (maybe do next year’s class too).
4.) Two days
5.) .055km
6.) .278m/s
7.) 54.7 m
8.) 2275m
Page 2 of 9
24.5 0
Midterm Review: Physics Practice
Unit 2: 1-Dimensional Motion
v f  vi  2ad
2
1.) Define:
 vector
 scalar
 displacement
 distance
 velocity
 speed
 acceleration
2
d  vi (t ) 
1
a (t 2 )
2
v f  vi  at
v
2.) Scalar or vector:
 distance
 displacement
 velocity
 speed
d
t
3.) A car goes 10 km to the north in half an hour. What was its average velocity in m/s
4.) A man is sledding in the new snow, going forward but gradually slowing down. Is velocity positive or
negative? Is acceleration positive or negative?
5.) A cart starting from rest rolls down a hill. In ten seconds the cart reaches 8 m/s. What was the
average acceleration?
6.) An ant walks 1 m north, two meters east, and then three meters south. What is the total distance?
What is the total displacement?
7.) The graph to the right represents the velocity of an object
traveling in a straight line as a function of time.
Describe the times at which (put them in an interval)
The object has a constant velocity:
The object has an increasing velocity:
The object’s velocity is greatest:
Lastly, does the object move in one or two directions? That is, does
it move forward only or forward and backward?
8.) A skateboarder slows down due to friction at a constant rate of 1 m/s2. If he stopped after 6 seconds,
what was his initial speed?
9.) A skier goes from 50 m/s to rest in 10 seconds. How far did it travel in that time if there was constant
acceleration?
Page 3 of 9
Midterm Review: Physics Practice
Unit 2 Answers
1).
 Vector- a measurement with magnitude and direction
 Scalar – a measurement with magnitude and no direction
 Displacement – a vector that measures the distance direction from the starting point to the ending
point.
 Distance – a scalar that measures all the steps/movement taken
 velocity – a measurement of how fast something moves and in what direction
 speed – a measurement of how fast something moves without giving direction
 acceleration – a vector that describes how fast something changes velocity in a particular direction
2.) scalar, vector, vector, scalar
3.) 5.56m/s north
4.) +, 5.) .8 m/s2 down the hill
6.) 6 m, 2 .83m southeast
7.) constant velocity 2 s to 6 s
increasing velocity 0 to 2 seconds and 6 to 8 seconds
velocity is greatest at 8 seconds
8.) 6 m/s
9.) 250 m forward
Unit 3: Dimensional/Free-fall
1.) In calculating a projectile motion problem, you find the x and y pieces of a projectile’s initial
velocity. You add them to your trig box as seen below. What is the overall velocity, v, of the
projectile?
v
3m/ s

4m/ s
2.) A ball is thrown up towards a basketball hoop at an angle of 45 degrees. When the ball peaks, it is
moving 4m/s to the right. What is the horizontal component of the velocity when the ball was initially
thrown?
3.) Which of the following describes the acceleration due to gravity: constant, 9.8 m/s2, downward,
negative, vector?
Page 4 of 9
Midterm Review: Physics Practice
4.) You are driving in a dune buggy on the moon (no air resistance) at a constant velocity to the right.
While you drive, you throw a computer straight up in the air. Where will the computer land when it
comes back down?
a.
b.
c.
d.
In the dune buggy
In front of the dune buggy
Behind the dune buggy
It depends on how hard you throw it
v f  vi  2ad
2
2
v f  vi  at
v
d
t
d  vi (t ) 
1 2
at
2
5.) Soccer Bob is standing still 38 meters away from the goal. He kicks a soccer ball with a speed of 20
meters per second at an angle of 30o above the horizontal directly towards the goal. The goal is 5 m
high. Will the soccer ball reach the goal in the air, go over the goal, or, fall short? Show the work.
Unit 2 Answers
1.) 5m/s at 36.8 degrees above the horizontal.
2.) 4 m/s
3.) all of them
4.) in the dune buggy
5.)
Page 5 of 9
Midterm Review: Physics Practice
Unit 4: Friction and Forces
1.) Name the two types of friction between two solid
objects. Which one is constant?
2.) For which type of friction is the coefficient of friction
generally lower? What does this mean in your own
words?
3.) Which of the following does not affect the force of
friction: the materials, the surface area, the normal force,
or the mass of the objects?
4.) Which has a higher coefficient of friction: ice and glass
or wood and metal?
5.) If an object is sliding to the left, which direction is the
friction force?
6.) A 5kg block of wood is on a table. If you apply 5 N of
pressure downward, what is the normal force on the
block?
7.) The coefficient of kinetic friction between wood and
sandpaper is about .7. If a block of wood is 10 kg what
horizontal force must be applied to keep the block at
constant velocity?
 Fx  max
 Fy  ma y
F f  Fn
v f  vi  at
v f  vi  2ad
2
2
1 2
d  vi (t )  at
2
v
d
t
8.) The coefficient of static friction between two objects
is .5. If the normal force between them is 10 N and a horizontal force of 10 N is applied to the top
object, what will happen?
9.) Is force a scalar or a vector?
10.) Draw a free body diagram of a 10 kg object being pushed 10 N to the left while on ice. What is the
net force on the object? What is the acceleration of the object?
11.) Draw a free body diagram of a 20kg object falling in the sky, experiencing an upwards air resistant
force of 15 N. What is the net force on the object? What is the acceleration of the object?
12.) A 100 kg cart that can freely roll is placed on level ground. On the left side, a child pushes the cart
rightward with a force of 14 N. On the right side, a playmate pushes the cart to the left with a force of
10 N. What is the net force? How fast will the cart be going after 10 seconds?
Page 6 of 9
Midterm Review: Physics Practice
Unit 4 Answers
1). Kinetic friction and static friction. Kinetic friction is constant
2). Kinetic friction has a lower coefficient of friction. This means that objects moving will generally easier
to slide than if the objects were not moving.
3.) Surface area
4.) Wood on metal
5.) Right
6.) 54N upwards
7.) 68.6N
8.) The objects will overcome the static friction and begin to slide.
9.) Vector
10.) Net force is 10 N rightward. The acceleration is 1m/s2.
11.) Net force is 181 N downward. The acceleration is 9.05 m/s2.
12.) 4 N rightward. .4m/s
Unit 5: Momentum
1.) A 25 kg person is running at a speed of 5.6 m/s. What is the person’s momentum?
2.) A 100 kg truck is traveling at 50 m/s. The truck then hits its breaks and slows to a speed of 30 m/s.
What is the impulse of the truck?
3.) A car initially has 600 kg∙m/s of momentum. It then hits a wall and comes to a complete stop. If it
takes the car 0.45 seconds to come to a complete stop what is the force on the car during the collision?
4.) A 120 kg Ford Focus is traveling eat at 5 meters per second when it collides with a 100 kg Ford
Mustang traveling west at 7 meters per second. If the two cars stick together what will their final
velocity be equal to?
5.) A 100 kg truck rear is traveling at 40 meters per second ends a 75 kg car traveling at 35 meters per
second. After the collision, the Truck is moving at 35 meters per second. How fast is the car moving
after the collision?
Page 7 of 9
Midterm Review: Physics Practice
Unit 5: Answers
1.) p  mv
p  25  5.6
p  140kg  m / s
2.)
p  p f  pi
p  m f v f  mi vi
p  100  30  100  50
p  300  500
p  200kg  m / s
3.)
p f  pi  Ft
0  600  F (0.45)
 600  F (0.45)
 1,333.33 N  F
4.)
pi  p f
mi vi  mi vi  m f v f  m f v f
120  5  100  7  220(v f )
1,300  220v f
v f  5.91m / s
5.)
pi  p f
mi v i  mi v i  m f v f  m f v f
100  40  75  35  100  35  75v f
4000  2625  3500  75v f
6,625  3,500  75v f
3125  75v f
v f  41.67m / s
Unit 6: Work and Conservation of Energy
1) A boy walks his 5 kg sled across his lawn by pulling on a rope that is at an angle of 38 degrees above
the horizontal. In order to do this, the boy provides a 10 N force. How much work does the boy do on
the sled?
2) A 540 kg car is traveling on flat ground at a speed of 73 meters per second. What is its kinetic energy
equal to?
Page 8 of 9
Midterm Review: Physics Practice
3) If a roller coaster gets stuck on top of a hill and isn’t moving, what type of energy does the roller
coaster have?
4) A spring has 45 J of EPE. If the spring is being compressed 0.7 meters, what is the spring constant
equal to?
5) Your 45 kg friend just won a million dollars and is jumping on her bed in joy. Right before she flies up
into the air, her mattress is compressed 0.5 meters. The spring constant of her mattress is 4,500 N/m.
How high does she fly up into the air?
Unit 6: Answers
1) W  Fd cos( )
W  10  5  cos(38)
2)
W  47.75 J
1
KE  mv 2
2
1
KE  540  (73) 2
2
KE  1,438,830 J
3) Gravitational potential energy (GPE). It’s on top of a hill so it has height. It’s not moving, so there is
no Kinetic Energy (KE), there are no springs involved so no Elastic Potential Energy (EPE) either.
4)
EPE 
1 2
kx
2
1
k (0.7) 2
2
1
45  k (.49)
2
45  .245k
183.67 N / m  k
45 
5) Ei  E f
EPE  GPE
1 2
kx  mgh
2
1
4,500(0.5) 2  45  9.8  h
2
562.5  441h
1.28meters  h
Page 9 of 9