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Forces and Motion Test Review
1. Define the following:
a. Momentum – a measure of mass in motion. Mass x velocity
b. Inertia – the resistance of an object to change in speed or direction of its
motion. The greater the mass the greater the inertia
c. Potential Energy – stored energy, or the energy an object has due to its
position or its shape. Two kinds are gravitational and elastic.
d. Friction – a force that resists motion between two surfaces that are
touching, produces heat
e. Kinetic Energy – energy of motion, faster movement=more kinetic energy
f. Mechanical Energy - the energy possessed by an object due to its motion or
position.
g. Centripetal force – any force that keeps an object moving in a circle. The
greater the acceleration, the greater the centripetal force.
h. Gravity – the force of attraction between two masses. The greater the mass,
the greater the gravitational force.
i. Contact Force – when one object touches another object
j. Force – a push or pull on an object
k. Work – the use of force to move an object some distance
l. Acceleration - the rate at which velocity changes over time
m. Net force – the overall force acting on an object when all the forces are
combined. Any unbalanced force will change the motion of the object.
n. Torque – a push or a pull in a circle
o. Gear ratio – a ratio of input to output.
p. Linear – Input gear moves in one direction, while the output gear moves in a
straight line, in one direction.
q. Reciprocating – Input gear moves in one direction, while the output gear
moves in a straight line, in two directions (back and forth).
r. Oscillating – Input gear moves in one direction, while the output gear moves in
a curved manner, in two directions (back and forth).
s. Rotary – Input gear moves in one direction, while the output gear moves in a
circular direction, in one direction.
2. For each of the following, write the formulas AND units.
Formula
Velocity
Acceleration
(see the Marble Flick lab)
Force
Momentum
Potential Energy
Kinetic Energy
Mechanical Energy
Velocity = Distance / Time
a
v final  vinitial
time
Force = mass x
acceleration
Momentum = mass x
velocity
GPE = mass x gravitational
acceleration x height
½ mv2
Potential Energy + Kinetic
Energy
Units - What is it
measured in?
m/sec with a direction
m/sec2
Newtons (N)
kg*m/sec
Joules
Joules
Joules
3. After school one day, Lindsay’s mom was driving her home. As they came to a
complete stop at a traffic light, Lindsay said, “We are accelerating a lot right now.”
Lindsay’s mom and sister looked at her like she was crazy. They said, “Lindsay,
accelerating means speeding up.” Who is right? Why?
Acceleration is the measure of the change in velocity. So, if the car is slowing down, the
velocity is changing. This means that the car would have a negative acceleration and
Lindsay is correct.
4. Explain how you could tell whether an object has positive, negative or zero
acceleration.
If an object was speeding up, it would have positive acceleration. If an object was slowing
down, it would have negative acceleration. If an object was sitting still or moving without
changing speed, it would have zero acceleration.
5. What are the three types of forces? Give an example of each.
* Contact force – when one object touches another object, ex) hitting a baseball
* Gravity – the force of attraction between two masses. The greater the mass the
greater the force, ex) when we jump, we come back down to the earth
* Friction – a force that resists motion between two surfaces that are touching, ex)
pushing a person on a chair
6. Forces have a size and a direction.
7. If an object is sitting still, then it is being acted upon by balanced forces.
8. If an object is sitting still and then begins to move, it is being acted upon by
unbalanced forces.
9. List Newton’s Laws below:
a. Newton’s 1st Law: ”Inertia” - Objects at rest remain at rest, and objects in
motion remain in motion with the same velocity….UNLESS acted upon by an
unbalanced force!
b. Newton’s 2nd Law: the acceleration of an object increases with increased
force and decreases with increased mass. F=MA
c. Newton’s 3rd Law: For every action, there is an equal and opposite reaction.
10. Newton’s 1st law states that objects in motion will stay in motion and objects at
rest will remain at rest at the same velocity, unless acted upon by an unbalanced
force. What are 2 things you would need to check for to see if an object is being
acted upon by an unbalanced force? These two “ways” should be able to be applied
in every situation.
In order for there to be an unbalanced force, the velocity has to have changed. Since
velocity is speed with a direction, an unbalanced force is acting upon an object if it is
changing in speed OR in direction.
11. What is inertia? How does an object’s inertia affect its velocity? How is this
connected to Newton’s 1st and 2nd laws?
Inertia is the resistance of an object to change in speed or direction of its motion. The
greater the mass an object has, the greater the inertia. So, an object that had a large
inertia would want to remain at rest more than an object with less inertia (1st law). Also,
an object with greater inertia would have a higher mass, which would decrease acceleration
(2nd law).
12. Explain how the egg was able to drop into the cup without breaking in our “Eggselent
Egg Drop” experiment. Be sure to discuss the balanced and unbalanced forces,
inertia, and gravity.
In the initial set up, the egg was resting in place on the top of the paper towel roll. This
means that it was being acted upon by balanced forces. When we hit the pie tin, we
created an unbalanced force, moving the pie tin. The egg had the greatest inertia so it
resisted moving the most of all the objects. In turn, the paper towel roll and the pie tin
moved, but the egg stayed in place. Once the paper towel roll and pie tin were gone, then
gravity acted up on the egg with an unbalanced force making the egg drop into the water.
13. Explain how the relationship between the number of rubber bands in the Newton’s
Car impacted the distance it traveled. Then explain how this relates to Newton’s 1st
law.
Newton’s 1st law states that an object at rest will remain at rest and an object in motion
will remain in motion with the same velocity unless acted upon by an unbalanced force. In
this case, the unbalanced force was the rubber band snapping back and the more rubber
bands, the greater the unbalanced force.
14. Explain how the relationship between the number of rubber bands in the Newton’s
Car and the distance it traveled relates to Newton’s 2nd law.
Newton’s 2nd law states that the greater the force, the greater the acceleration, so the
cars went farther. The more rubber bands there were on the car, the farther the cars
traveled. This relates to Newton’s 2nd law because with more rubber bands, there was
more force.
15. Explain how the relationship between the number of rubber bands and the distance
the Newton’s Car traveled relates to Newton’s 3rd law.
The greater the number of rubber bands, the greater the distance that the car traveled.
Newton’s 3rd law states that every action has an equal and opposite reaction. With more
rubber bands, there was more force applied to the weight. This gave a greater action, and,
in turn, a greater reaction.
16. What is centripetal force? How does acceleration relate to the amount of
centripetal force? Give two examples where you have seen centripetal force in your
life.
Centripetal force is any force that keeps an object moving in a circle. The greater the
acceleration, the greater the centripetal force. A washing machine, ice skaters spinning,
and spinning water around in a bucket are examples of centripetal force.
17. Define momentum. Explain why dropping a tennis ball on a basketball will cause the
tennis ball to go flying but dropping a basketball on a tennis ball causes little to no
reaction.
Momentum is mass times velocity. When a tennis ball is dropped on a basketball it goes
flying because the basketball has a greater mass. This means that it has more momentum
when it drops. The energy created by this momentum is then transferred into the tennis
ball making it fly. When the basketball is dropped on the basketball, less energy is
transferred to it from the tennis ball because the tennis ball has less mass and therefore
less momentum.
18. Why do you think a car’s engine needs oil to work?
Oil reduces the friction in an engine. As friction produces heat, without oil, an engine
would overheat.
19. If you try to push a heavy box as hard as you can, but it stays still, has work been
done on the box? Why?
No work has been done on the box because it did not move.
20. Refer to the Rubber Band Cannon Lab that we completed and answer the following:
a.) What two types of potential energy were displayed in the lab? Define each kind of
potential energy and give an example of where it was shown in the lab.
Gravitational potential energy was displayed as the rubber band cannon was placed on a
chair. It had the potential to fall down. In addition, the rubber band itself had a lot of
gravitational potential energy when it was at the top of its arc.
Elastic potential energy was shown when the rubber band was pulled / stretched back in
the rubber band cannon.
b.) Draw the path the rubber band took when shot at a 40˚ angle. Then, label the
points on the path where the rubber band had the most AND least potential AND
kinetic energy.
High GPE
Increasing PE
Decreasing KE
Increasing KE
Decreasing PE
Just before landing = High KE & Low PE
Before release = High EPE & Low KE
Scientific Writing
Mr. Bezeau was playing in his garage one afternoon and discovered how to create a
matchbook rocket. He wrapped the head of a match in tinfoil, place a small angled hole
with a straight pin, and set it on a paper clip that served as the launch pad. He then lit a
match under the tinfoil. The match began to burn inside the tinfoil and then shot off like
a rocket! Mr. Bezeau wanted to see if the size of the hole made an impact on the distance
the rocket went. So, he set off three rockets with increasingly bigger holes. Figure A
below represents his results. Explain the relationship between the size of the hole poked
in the tinfoil and the distance the rocket went.
Figure A.
The following questions refer to Figure A above.
What units are the distance of the rocket measured in? cm
What is the dependent variable in this graph? Distance of launch
What is the independent variable in this graph? Size of the hole
If Mr. Bezeau poked a hole that was even smaller than the “Small Hole” referenced on the
graph, what distance would you predict the rocket to travel? ~125 cm (ans will vary)
What is the scale interval on the y axis? Each line represents 50 cm
Mr. Bezeau read his “Forces and Motion” notes from science class and repeated the
matchbook rocket experiment. This time, he wanted to see if the amount of tinfoil used
made an impact on the distance the rocket went. So, he set off three rockets with
increasingly bigger masses. Figure B below shows his lab results. If Mr. Bezeau’s teacher
asked him to explain the relationship between the amount of tinfoil used and the distance
the rocket went. Write the response that Mr. Bezeau should write.
Figure B
Mass
Distance
10 g
150 cm
20 g
80 cm
30 g
50 cm
The following questions refer to Figure B shown above:
What is the independent variable in the chart? The mass of the rocket
What is the dependent variable in the chart? The distance traveled
If you were to graph these results, what data would be placed on the x axis? The mass of
the rocket
If you were to graph these results, what data would be placed on the y axis? The distance
traveled
If a rocket that had a mass of 25 g, what distance would you predict the rocket would
travel? ~65 cm