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7th Grade Science – Forces, Motion, and Energy Book
Matter in Motion
Why is the point of reference important when describing motion?
It is important to have a point of reference in order to describe the
motion of an object because the point of reference is something that is
immobile and you can use it to compare the motion of another object to say
that it is moving and the way that it is moving.
Write the equation for determining the AVERAGE speed of an object:
What is the difference between speed and velocity?
The difference between speed and velocity is that speed is just a rate
of motion and velocity is a rate of motion and a direction.
7th Grade Science – Forces, Motion, and Energy Book
How is acceleration represented on a graph?
Positive acceleration on a speed v. time graph is represented as a positive slope (uphill).
Negative acceleration on a speed v. time graph is represented as a negative slope (downhill).
Write down the equation to find the AVERAGE acceleration of an object:
What is unique about an object in a circular motion?
It is in constant acceleration as it is constantly changing its direction –
circular motion not linear motion
Define the following terms: motion, velocity, speed, acceleration, force, newton, net force, friction,
gravity, weight, mass
What are three examples of forces acting on objects in the room around you?
1.
2.
3.
Answers may vary – example: light hanging from the ceiling is pulling on the ceiling.
7th Grade Science – Forces, Motion, and Energy Book
Finish this sequence:
To find the net force of forces acting in the same direction, you ___
add__ them.
To find the net force of forces acting in the opposite direction, you ____
When a net force equals zero, the forces are called _____
subtract__ them.
balanced___.
When a net force does not equal zero, the forces are called _____
unbalanced___.
How does force effect friction?
The more force that is applied, pushing the objects together, then the
more friction that is produced.
How does the surface’s roughness affect friction?
The rougher the surface is – the more friction that is produced as those
surfaces pass by each other. Think of two pieces of sandpaper rubbing
together.
The smoother the surfaces are the less friction there will be between
the two surfaces. Think of two regular sheets or writing paper rubbing
against each other.
Work on friction push/pull lab.
7th Grade Science – Forces, Motion, and Energy Book
What are two types of friction? Explain each.
Kinetic Friction – the friction of objects that are in motion.
**There are two types of friction:
Rolling Friction – the friction of objects that are rolling past each other. (Wheels) This
type of friction is lower than sliding – think about rolling something vs. sliding the
object when moving it, which is easier?
Sliding Friction – the friction of objects that are sliding past each other.
Static Friction – the friction of objects that are not moving. You must overcome this force to make an
object move. It is what keeps objects from sliding off of tables and desks when you set them down.
Speculate what the world would be like without friction. (2-3 ideas)
Various ideas – could not walk, cars would not grip the
road, could not pick up objects, …
How can friction be reduced? (2-3 ideas)
 Use lubricants – oil, grease, & waxes
 Reduce the force that is pushing the surfaces together
 Smooth the surfaces that are in contact
7th Grade Science – Forces, Motion, and Energy Book
How can friction be increased? (2-3 ideas)
 Increase the roughness of the surfaces that are in contact
 Increase the force pushing the objects together
What is the relationship between mass and gravity? How do they affect each other?
GRAVITY RELIES ON MASS
The amount of mass determines the amount of gravitational force
acting on an object. The more mass something has, the more gravitational
force acting on the object. The less mass an object has the less gravitational
force acting on an object.
Why do you not feel the gravitational forces that are acting on you by other objects?
You do not feel those forces because of the closeness of Earth to you
and the mass of the Earth compared to those other objects.
What did Sir Isaac Newton add to the understanding of gravity?
Sir Isaac Newton was the person the related the forces that drew objects to the
Earth (apple falling – constant cycle of the moon) to one force – GRAVITY. He was also
the person that related all object in the universe experience gravity due to their
masses.
7th Grade Science – Forces, Motion, and Energy Book
Explain the two parts of the Law of Universal Gravitational
1. Gravitational Force Increases as Mass Increases –
See pictures in book on page 22 & 23
As the mass of an object increases, the gravitational forces between them
increase as well. As the mass of the objects decrease, the gravitational forces
between them decrease as well.
2. Gravitational Force Decreases as Distance Increases –
See pictures in book on page 22 & 23
As the distance between objects increases, the gravitational forces between
them decrease. As the distance between objects decrease, the gravitational
forces between them increase.
Are weight and mass the same thing? Explain.
NO they are not the same thing. Mass will not change – no matter
where you go – but your weight will change as you go from place to place
where gravity changes (i.e. from planet to planet, on a tall mountain, etc.)
What is the unit for mass? For Weight?
Weight – lbs (pound), kg (this is a true error because kg is for mass)
Mass – mg, g, kg
7th Grade Science – Forces, Motion, and Energy Book
Forces and Motion
Define the following: terminal velocity, free fall, projectile motion, inertia, momentum,
How are gravity and acceleration related?
What is the rate of acceleration of an object due to the gravity of Earth?
What is the formula to find the velocity of a falling object due to gravity?
Explain how air resistance affects falling objects.
7th Grade Science – Forces, Motion, and Energy Book
Explain what terminal velocity is. (Go beyond the definition/Use your own words)
What do we know about objects that fall in a vacuum?
What do we know about objects in space that are orbiting the planet? Explain.
Why does the moon not fly away from the Earth?
7th Grade Science – Forces, Motion, and Energy Book
What are the components of projectile motion? Draw a diagram and label the components.
What is Newton’s 1st Law of Motion?
What is Newton’s 2nd Law of Motion?
7th Grade Science – Forces, Motion, and Energy Book
What is Newton’s 3rd Law of Motion?
How does friction affect Newton’s 1st law of Motion?
How does mass and inertia work with Newton’s 1st Law of Motion?
What is the formula for finding acceleration? Show both variants.
7th Grade Science – Forces, Motion, and Energy Book
Explain how the force pairs act on different objects. Use an example if necessary.
Why are some of the action-reaction pairs difficult to see?
Write down the formula to calculate the momentum of an object:
Write down the Law of Conservation of Momentum:
7th Grade Science – Forces, Motion, and Energy Book
What happens to the momentum of objects that collide with each other and stick together?
What happens to the momentum of objects that collide with each other and bounce off each other?
How does the law of conservation of momentum relate to Newton’s 3rd Law of Motion?
Work on Newton Lab Stations
Forces in Fluids
Define the following: fluid, pressure, pascal, atmospheric pressure, buoyant force,
Archimedes’ principle, Bernoulli’s principle, lift, thrust, drag, Pascal’s principle,
Write down the formula for finding pressure:
7th Grade Science – Forces, Motion, and Energy Book
What causes pressure within objects?
What properties do a liquid and gas share that affect pressure?
Why are bubbles spherical in shape?
What is the force on you called that is caused by a column of air above you?
Why does this force not crush you?
7th Grade Science – Forces, Motion, and Energy Book
What is the correlation of pressure and depth? What is the correlation of pressure and altitude?
Why does the density of the fluid matter in the pressure it exerts?
How does a difference in pressure affect fluid flow? Give an example.
7th Grade Science – Forces, Motion, and Energy Book
Looking at Archimedes’ principle, does the weight of the object affect the buoyant force? Explain.
Explain how objects float, sink, or buoy up/down in a fluid.
Explain the floating and sinking of an object in air.
7th Grade Science – Forces, Motion, and Energy Book
Work on floating canister lab.
How do ships that are made of heavy metals float, when metals are denser than water?
Explain how submarines can float and sink in the water.
How do fish change their depth in water?
What do we know happens to the pressure of a fluid as the velocity of the fluid increases?
What do we know happens to the pressure of a fluid as the velocity of the fluid decreases?
7th Grade Science – Forces, Motion, and Energy Book
Draw a diagram of an airplane wing and label what forces are at work.
Explain the relationship of wing size of an airplane to the thrust of the airplane’s engines.
How does Bernoulli’s Principle work during a baseball pitch?
Explain what turbulence is and how it affects the lift of an airplane.
7th Grade Science – Forces, Motion, and Energy Book
Give some more examples of Pascal’s principle that people use in everyday life.
1.
2.
3.
Work and Machines
Define: work, joule, power, watt, machine, work input, work output, mechanical advantage,
mechanical efficiency, lever, pulley, wedge, screw, wheel & axle, compound machine, inclined
plane
What is the difference between applying a force to and object and doing work on an object? Explain.
Is pushing an object up an inclined plane receiving the same amount of work as if it was pulled straight up the
edge of a cliff – both items are going to the same altitude – if so explain.
7th Grade Science – Forces, Motion, and Energy Book
Work on diagram similar to page 95.
Write down the formula for finding work:
Write down the formula for finding power:
Scientifically speaking, what does it mean if someone says that their machine is more powerful than a
competitor’s? Explain.
Are all machines very complex pieces of equipment?
7th Grade Science – Forces, Motion, and Energy Book
What is a Machine?
What is the primary purpose of a machine?
What are the two main forces involved with a machine?
Do machines change the amount of work that is done from the input to the output? If no, then what factor is
changed?
What trade off is made in a machine to help make things seem “easier?”
7th Grade Science – Forces, Motion, and Energy Book
Write down the formula for finding the mechanical advantage of a machine:
Write down the formula for finding the mechanical efficiency of a machine:
Will the mechanical efficiency of a machine ever be 100% or perfect? Why?
When looking at the formulas for mechanical advantage and mechanical efficiency, the difference between
them is:
Mechanical advantage compares: _________________________________________
Mechanical efficiency compares: __________________________________________
7th Grade Science – Forces, Motion, and Energy Book
Types of Machines
Make a diagram of the different types of levers and the comparison of them. Use pictures and
force diagrams (like in the book) to show their differences.
Make a diagram – and show in class – the different classes of pulleys. Use pictures/diagrams to
show their differences.
Make diagrams of the following to explain them: wheel & axle, inclined plane, wedge, & screw.
Make a flipbook/foldout of all of the types of machines and how to find the mechanical
advantages of them.
What is a compound machine? What happens to the mechanical efficiency of a compound machine as it gets
more complex?
7th Grade Science – Forces, Motion, and Energy Book
Picture
Force Diagram
First-Class Lever
Second-Class Lever
Third-Class Lever
Fixed Pulley
Moveable Pulley
Block and Tackle
7th Grade Science – Forces, Motion, and Energy Book
Energy and Energy Resources
Define the following: energy, kinetic energy, potential energy, mechanical energy, energy
conversion,
What is Energy?
What is the relationship between work and energy?
Energy is the ability to do work. They are both expressed in
Joules (J), which is a measure of work.
Write down the equation for finding kinetic energy:
Kinetic energy is the energy of motion. m = mass (kg); v = velocity (m/s);
Units are in Joules (J)
Write down the equation for finding the gravitational potential energy of an object:
This is the energy due to position of an object. Weight (N); height (m); Units
are Joules (J)
What key component can you change to increase or decrease the kinetic energy of an object?
Velocity because it has the greatest impact on the kinetic energy of an
object (velocity is squared).
7th Grade Science – Forces, Motion, and Energy Book
What key component can you change to increase or decrease the gravitational potential energy of an object?
You can change the height of the object.
How do you measure that one component in potential energy?
You would measure that height from one established point on Earth. (i.e. –
is it on top of the desk or from the floor…)
Write down the equation for finding the mechanical energy in an object:
Units: Joules (J)
Units
Label the points of maximum potential and kinetic energy
7th Grade Science – Forces, Motion, and Energy Book
Briefly describe the following energy types
Thermal Energy
Chemical Energy
Electrical Energy
Sound Energy
Energy of the motion of particles.
There are two factors for thermal energy – the
temperature and the number of particles.
Potential energy – it is the energy of a
compound that changes as the atoms are rearranged. This energy is released through
chemical reactions.
The energy of moving electrons (kinetic
energy). Can be potential energy when nothing
is plugged in to the electrical source.
This is the kinetic energy of moving particles
within a substance (solid, liquid, gas). This is
caused by the vibrations of a substance
Light Energy
The kinetic energy of electrically charged
particles – you DO NOT need to have a
substance for this process to occur (how light
travels through space).
Nuclear Energy
The energy that stored in the nucleus of an
atom. This is released through the change in
an atom’s nucleus.
Fusion – combining 2 nuclei
Fission – splitting a nucleus
7th Grade Science – Forces, Motion, and Energy Book
Energy Conversions
What happens to the energy of a moving object as it travels – as in a rollercoaster or a pendulum?
The energy of an object is converted from one form to another (i.e.
– kinetic to potential energy in the pendulum)
Explain the energy that is stored in a stretched rubber band.
By changing the shape of the rubber band, the energy that is put
into the band is stored as elastic potential energy.
How do animals get energy from the food they eat?
Animals get the energy from their food by breaking the chemical
bonds in the foods that we eat to power our bodies.
How do plants get energy? Explain.
Plants use light energy from the sun in photosynthesis to create food for
the plants which is used or stored and the plants also create oxygen. The
energy in the food is a form of chemical energy. If the energy is followed
from the plant, it can eventually be traced to the sun.
7th Grade Science – Forces, Motion, and Energy Book
What makes energy conversions important?
Energy conversions are important because they are important
for life and to make our lives easier for us in many different
ways. **All energy on Earth traces back to light energy of the
sun.**
Give some examples of energy conversions YOU use daily.
Eating – chemical energy to thermal or kinetic energy
Furnace – thermal energy from electrical or chemical
Dishwasher – electrical to kinetic energy
Fireplace/Wood stove – thermal from chemical energy
What can machines do with energy?
Machines use energy to make work easier. Machines can change
the forces and distance involved in doing the work. Machines also
convert energy into the form that we need.
7th Grade Science – Forces, Motion, and Energy Book
What happens to some of the energy used by a machine?
Some of the useful energy is converted into thermal energy
because of friction.
What is a closed system? What do we know about the total energy in a closed system?
A closed system is a group of objects that transfer energy between
themselves. The total energy in a closed system stays the same, the
energy is just being converted from one form to another.
What is the Law of Conservation of Energy?
Energy cannot be created or destroyed; energy is converted from
one form to another.
Can an energy conversion occur without some of the energy being converted to thermal energy? Give an
example.
No, because there is always going to be some form of friction
converting the useful energy to thermal energy.
** useful energy refers to the energy you want at that moment
7th Grade Science – Forces, Motion, and Energy Book
What is a perpetual motion machine? Do they exist? Why?
A perpetual motion machine is a machine that only needs energy
applied to it to get it started and will always put out the same
amount of energy used to start it. These machines do not exist
because of friction which converts some energy to thermal energy.
How do engineers try to make the most out of their machines converting energy? Give an example.
Engineers want the amount of useful energy at the end of a conversion to
be close to the amount of energy put into the machine (at the beginning of
the conversion). Ex. Cars are being made more aerodynamic
Energy Resources
What is an energy resource?
An energy resource is a natural resource that can be converted into
other forms of useful energy.
What are nonrenewable resources?
Nonrenewable resources are resources that cannot be replaced or
are replaced slower than they are used (millions of years).
Ex. Fossil fuels – coal, oil & natural gas
7th Grade Science – Forces, Motion, and Energy Book
Give 4 examples of a nonrenewable resource.
1. Coal
2. Nuclear Fuel
3. Petroleum (oil)
4. Natural Gas
What are most fossil fuels used for the U.S.?
Most fossil fuels are used for the generation of electrical energy.
Diagram or list the process of making electricity from fossil fuels.
7th Grade Science – Forces, Motion, and Energy Book
What is a renewable resource?
A natural resource that is replaced as quickly as it is used.
List 5 different renewable resources:
1.
3.
Solar Energy
Water
2. Wind
4. Geothermal – heat from under the
surface of the Earth
5. Biomass – wood, plants, waste
How do we choose the right source (renewable v. nonrenewable) to use?
It depends on what we need the energy for, how much energy we
need and what is available.
7th Grade Science – Forces, Motion, and Energy Book
7th Grade Science – Forces, Motion, and Energy Book