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Review Sheet/Study Guide for Unit 5 Test: ANSWER KEY!!!
Energy, Forces, Speed, Newton’s 1st Law
All answers MUST be written on a separate sheet of paper!
Use your class notes- they are a very valuable resource!
Part 1. Energy #1-10
Due: __________________
(Study your “Kinetic and Potential Energy” graphic organizer notes, your “KE/PE packet”, and your Energy
Quiz)
1.
What is the definition of energy? What units do we measure energy in? How do we abbreviate these
units?
Energy is the ability to do work. We measure energy in Joules. It is abbreviated J (capital J).
2.
What is the definition of work? What does work require? What is the formula for calculating work?
Work is the product of force and distance. Work requires motion (the object must move!) The formula
for calculating work is force times distance.
3.
What is the relationship between kinetic and potential energy? Give one real life example of this
relationship.
The relationship between kinetic and potential energy is that as potential energy decreases, kinetic
energy increases (they are opposites, or have an inverse relationship.) A real life example of this is a
ball falling off of a high shelf. Your muscles moved the ball up to the shelf and stored potential energy
in it. As it fell, the potential was converted to kinetic as it went faster and faster.
4.
List 2 examples of objects with kinetic energy. List 2 examples of objects with potential energy.
KE: a car speeding down the highway, a fish swimming in the ocean. PE: the flag at the top of the
flagpole, a school bus waiting at the light at the top of the mountain by Utopia Deli.
5.
How do we calculate kinetic energy? (What is the formula?)]
The formula to calculate KE is KE= ½ m v2 m is mass, v is velocity.
6.
What is the kinetic energy of a 50 kg car that is moving at 10 m/s? (write the formula, plug in
numbers, write the answer with units)
KE=1/2 m v2 KE= ½ x 50 x 102 KE= 2500 J
7.
How do we calculate gravitational potential energy? (What is the formula?)
The formula to calculate GPE is GPE= m g h m is mass, g is gravity, h is height.
8.
What is the gravitational potential energy of a 4 kg tennis ball dropped from a height of 5 meters.
(The force of gravity is 9.8 m/s2) (write the formula, plug in numbers, write the answer with units)
GPE= m g h GPE= 4x9.8x5 GPE= 196 J
9.
What is the relationship between energy and work? (How are they related?)
Without energy, you cannot do work! (Energy is the ability to do work. See #1)
10.
Restate the Law of Conservation of Energy.
The law of conservation of energy states that energy cannot be created or destroyed. It can only be
transformed from one form to another. (for instance, from KE to PE, or from movement to heat)
Part 2. Forces/Speed #11-27
Due: __________________
(Study your “Forces and Motion” notes, “Speed Demos/Notes”, the “Speed and Velocity” graphing, the
“Speed Calculations” homework, and your Forces/Speed quiz)
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24.
What is a force? Give two examples of forces you encounter everyday.
A force is a push or a pull that can change an object’s velocity. Forces we encounter everyday are
friction, air resistance, gravity, and the pushes and pulls of our hands and feet. (many more!)
What units do we use to measure force? How do we abbreviate these units? Who is the unit named
after?
We measure force in newtons. It is abbreviated N (capital N). The unit is named after Sir Isaac Newton.
What is net force?
Net force is the overall, or total of all forces acting on the object.
What is a balanced force? What is the net force equal to when forces are balanced? What happens to
an object when forces are balanced?
A balanced force is one that causes no change in an object’s motion. The net force is zero. The object
will not CHANGE its movement (It will stay stopped, or stay moving the way it was.)
What is an unbalanced force? ‘
An unbalanced force is one that will cause a change in an object’s motion. The net force is not zero.
The object will experience a change in its motion (speed up, slow down, start moving or stop moving.)
When unbalanced forces are acting in the same direction, what do we do to them (mathematically)?
When unbalanced forces act in the same direction, we add them together. (find the sum)
Two people are pushing on a piano. Person A is pushing to the right with a force of 20N. Person B is
pushing to the right with a force of 35N. What is the net force on the piano? What will the piano do?
The net force is 55 N to the right. The piano will move to the right.
When unbalanced forces are acting in different directions, what do we do to them (mathematically)?
When unbalanced forces act in different directions, we subtract them. (find the difference)
Two people are pushing on a desk. Person A is pushing to the right with a force of 50N. Person B is
pushing to the left with a force of 25N. What is the net force on the desk? What will the desk do?
The net force is 25 N to the right. The desk will move right, since that force was large and “wins”.
What is speed? What is velocity? How are they different?
Speed is the quickness of a trip, or distance divided by time. Velocity is speed AND direction. They are
only different because velocity also includes WHICH WAY the object is traveling.
A football field is 100 yards long. If it takes a person 20 seconds to run its length, how fast (what
speed) were they running? (write the formula, plug in numbers, write the answer with units)
s=d÷t
s=d÷t
s= 5 yards per second
The pitcher’s mound in baseball is 85 m from the plate. It takes 4 seconds for a pitch to reach the plate.
How fast is the pitch? (write the formula, plug in numbers, write the answer with units)
s=d÷t
s = 85 ÷ 4
s= 21.25 meters per second
Jane drives at an average speed of 45 mph on a journey of 180 miles. How long does the journey take?
(write the formula, plug in numbers, write the answer with units)
s=d÷t
45 = 180 ÷ t (Set up a ratio!)
t = 4 hours
Nikki has to travel a total of 351 miles. She travels the first 216 miles in 4 hours.
(a) What is her average speed for the first part of the journey? (write the formula, plug in numbers,
write the answer with units)
s=d÷t
s = 216 ÷ 4
s = 54 miles per hour
HONORS ONLY - Her average speed is the same for her entire journey.
(b) How long does the whole journey take? (write the formula, plug in numbers, write the answer
with units)
s=d÷t
54 = 351 ÷ t t= 7.8 hours
Use the graph to answer questions 25 – 27. It shows the
data from a turtle swimming in the Pacific ocean.
25.
Determine the slope of the line (show your work!):
slope = rise ÷ run
26.
slope = 6 ÷ 3
slope = 2
What speed is the turtle is traveling at?
2 meters per second
27.
At 27 seconds, how far did the turtle swim?
s=d÷t
2 = d ÷ 27
d= 54 meters
Part 3. Newton’s 1st Law of Motion & Friction #28-34 Due: ________________
(Study your “Newton’s first law notes”, your “Friction and How Things Move” notes, your “Coin Caper” activity, and
your “Newton’s 1st Law and Friction” practice quiz)
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Restate Newton’s 1st law of motion. (Remember, your OWN words are ok!)
An object at rest will stay at rest unless acted on by an unbalanced force. An object in motion at a
constant velocity will stay at that velocity unless acted on by an unbalanced force.
Give an example of an object at rest and an object in motion obeying Newton’s 1 st law of motion.
(What is it doing? Why does it keep doing that?)
A book sitting on the table will stay there until a force is applied to move it.
A ball rolling across the floor will slow down because an unbalanced force (Friction) causes its velocity
to change.
Why do objects slow down on Earth? (Why don’t they keep going forever?)
Objects slow down on Earth because of friction. They rub on surfaces they touch because of gravity
pulling them down, and also when they “rub” on the air and experience air resistance.
What is inertia? Give a real-life example of inertia.
Inertia is a property of matter (a tendency). Matter resists a chance in its motion.
A real life example of inertia is why school buses are so slow. They are very large and have a lot of
inertia to overcome to get moving. All the atoms of the school bus do not “want” to move, they “want”
to keep doing what they are doing, stay at rest.
What are the 4 main categories of friction? List an example of each.
Static friction- (friction of things at rest but a force is applied) – A heavy dresser is hard to get sliding
across the floor.
Sliding friction- (friction of things sliding past each other) – The force that fights against moving the
heavy dresser once you have it sliding. It is what makes it hard to move!
Rolling friction- (friction on a wheel or round object rolling) – the force that slows down the skateboard
as you coast down the hallway.
Fluid friction- (friction on any object moving through a liquid or gas) – the force that pushes on your
hand when you hold it out the car window.
33.
Draw a skateboard moving to the left. Identify (with arrows) at least 3 forces acting on the skateboard.
Don’t forget to label the type, size, and direction of the forces (arrows)!
gravity
34.
Draw an example of an object experiencing projectile motion. Explain why the object travels in that
path. What is the name of the shape the object travels in?
An object travels in a PARABOLA during projectile motion because of unbalanced forces. The first push
makes it move up and forward. After it is moving, gravity pulls down and air resistance slows it down,
so it curves back to the ground.