Unit Big Idea: Unbalanced forces cause changes in the motion of objects, and these changes can be predicted and described.
Lesson 1 – Motion and Speed
Essential Question: How are distance, time, and speed related?
By the end of this lesson, you should be able to analyze how distance, time, and speed are related.
- Position – describes the location of an object
- can compare its position with the location of something else (ex: I live in the house next to the
Food Lion or turn left on the street in front of the big post office)
- Reference Point – a location you are comparing other locations to.
- ex: I live in the house next to the Food Lion – the reference point is the Food Lion
- ex: turn left on the street in front of the big post office – the reference point is the big post office
- Motion – change in position over time
- can either be observed by seeing the object move or by seeing the where it is one moment and
noticing that it’s in a different location later on
- Distance is measured in different ways depending on what information you want.
- If you want to know the straight-line distance between two positions, like from Shelburne
Middle School to Lee High School, you would measure the distance with a straight line on a
map. This is the total distance from one location to another.
- If you want to know the total length of the path/road you must take to get from Shelburne
Middle School to Lee High School you would measure each road and turn until you get there.
This distance is usually much longer than the straight-line distance. Since there is no easy path
to get to Lee High from Shelburne, you must wind your way through town to get there. The
distance will be much longer than the actual straight-line distance on a map between the two
schools.
- distance is measured in units of length – meters (m); longer distances are measured in
kilometers (km) and shorter distances in centimeters (cm).
- in the US, distance is measured in miles (mi), feet (ft), or inches (in) but that is not part of the
metric system and we won’t be using it in science class .
- speed – measures how far something moves in a given amount of time
- how quickly/slowly an object changes its position
- ex: it takes you 2 minutes to walk from Mrs. McCauley’s classroom to science class or it takes
you 3 minutes to get from gym class to your locker.
- average speed – way to calculate the speed of an object that may not always be moving at a
constant speed – describes the speed of an object over a stretch of time.
- it takes 20 seconds to walk from the gym to the stairs, 40 seconds to get up the stairs,
then 2 minutes to get from the stairs to your locker since you’re now walking and talking
with a friend. Instead of looking at how your speed changes over the time it takes to get

from the gym to your locker, you look at the overall average speed of 3 minutes to get
from the gym in the morning to your locker.
- speed can be calculated by dividing the distance an object travels by the time it takes to cover
the distance.
Average = distance (
speed ( s ) time ( t ) d ) s = d
t
- if two objects travel the same distance, then the one to get there first has a greater speed
- ex: two students running the mile in gym class have the same distance to travel
– a mile – the student to get to finish first ran faster than the student that finished
second.
- an object with a greater speed will travel a longer distance in the same amount of time
than an object with a lower speed will.
- ex: your gym teacher has you run around the track for 5 minutes to warm up.
The student running the fastest will run around the track more times for a greater
distance than a student running at a slower pace. By the end of the 5 minutes, the
faster student will have run more laps around the track than the slower student.
- standard unit for speed is meters per second (m/s) but can also be done in kilometers per
hour (km/h)
- US calculates speed in miles per hour (mi/h or mph) but we won’t be using that in
science class since miles are not part of the metric system.
- graphing constant speed to show motion -
- distance-time graph – plots the distance the object traveled against time
- X-axis is the time in seconds, minutes, or hours
- Y-axis is the distance in meters, kilometers, or centimeters
- if an object is moving at a constant speed the graph is a straight line
- the slope of the line is the average speed of the object
- to calculate the average speed for a time interval, divide the change in distance by the
change in time [rise (change in y) over run(change in x)]
- graphing changing speed:
- General Everyday Terminology:
- accelerating – getting faster at a constant speed
- decelerating – getting slower at a constant speed
- the steeper the slope of the line the faster the object is accelerating or decelerating
- a flat line shows that the object is not moving
- vector – number that has both size and direction
- velocity – speed in a specific direction (north, east, south, west)
- two objects can have the same speed but different velocities if they’re going in different
directions
- average velocity is calculated from a straight-line distance from the starting point to the end

point (displacement)
- ex: if you walk from your science class to lunch at an average velocity of 3 cm/min south then
walk back to your science classroom at 3 cm/min north, your average velocity would be
0 cm/min since you returned to your starting point
Lesson 2 Acceleration
Essential Question: How does motion change?
By the end of this lesson, you should be able to analyze how acceleration is related to time and velocity.
- Acceleration - measures the rate of change in velocity or rate at which
velocity changes
- acceleration refers to any change in speed – increasing or decreasing (deceleration)
- an object can accelerate if it’s speed or its direction or motion changes or both
- a small change in velocity can have a large acceleration if the change happens quickly
- a large change in velocity can be a small acceleration if it happens slowly
- the unit of measure for acceleration is meters per second squared (m/s 2 )
Average = [final velocity ( v
2
) – starting velocity ( v
1
)]
Acceleration ( a )
- Accelerating Objects change speed when: time ( t ) a = (v2 – v1) t
-
- positive acceleration negative acceleration
down)
- increase in velocity (from small velocity to larger velocity)
– decrease in velocity (from larger velocity to smaller velocity - slowing
- acceleration of an object that is decreasing its speed will have a negative velocity since its going
from a faster speed to a slower speed. This means acceleration ( a) in the equation above will be
a negative number.
- When acceleration and velocity are going in the same direction the speed increases.
- When acceleration and velocity are going in opposite directions, acceleration works against the
initial motion and the speed decreases.
- Acceleration also tends to decrease when an object is going uphill and increase
- An object that is changing its direction of motion will accelerate even if it does not speed up or slow
down.
- centripetal acceleration - acceleration in circular motion
- when an object travels in a circular motion it is always changing direction so it’s always
accelerating

Lesson 3 – Forces
Essential Question: How do forces affect motion?
By the end of this lesson, you should be able to describe different types of forces and explain the effect force has on motion.
- force – a push or a pull
- has both a size and a direction
- can cause an object to change its speed or direction but doesn’t always cause an object to move
- unit is Newton (N)
- a force can act directly on an object
-
- contact force friction
– force exerted when two object touch or come in contact with each other
is an example of a contact force between two objects
- friction between the tires of a car and the road keep the car on the road when it goes
around a curve
- a force can act on an object from a distance
-
- gravity acts on an object from a distance magnetic force can push or pull an object from a distance as well
- net force – combination of all the forces acting on an object
- when forces act in the same direction, add them together to get the net force
- when forces act in opposite directions, subtract the smaller one from the larger one to figure out
the net force
- 0 net force shows the forces are balanced against each other & won’t cause a change in motion
of either a moving object or a nonmoving object
- unbalanced net force (not 0) causes a change in motion – either change in speed, direction, or
both
- acceleration is the change in motion from an unbalanced net force
- 1 st LAW OF MOTION OR LAW OF INERTIA – An object at rest stays at rest, and an object in
motion stays in motion at the same speed and direction, unless it experiences an unbalanced force.
- In simple words: an object at rest stays at rest and an object in motion stays in motions unless
something comes along and causes a change
- inertia – tendency of an object to not change its motion
- the object in motion will stay in motion at the same speed and direction (velocity) unless an
unbalanced force acts on it and changes the speed or direction, or both
- 2 nd LAW OF MOTION
– The acceleration of an object depends on the mass of the object and the
amount of force applied
- In simple words: if two object are different masses and the same pushing force is used, the

smaller mass will have a greater acceleration than the larger mass
- Force equals mass times acceleration
Force = mass x acceleration
- When going up a hill in a roller coaster, gravity works against the upward acceleration force of
the roller coaster
- When going down the hill, the acceleration force and gravity work in the same direction and the
seat of the roller coaster doesn’t support your full weight so you feel as you’re flying when you
come out of your seat.
F = ma
- 3 rd LAW OF MOTION – Whenever one object exerts a force on a second object, the second object
exerts an equal force on the first AKA: all forces act in pairs
- In simple words: when you push on something, it actually pushes back against you
- action forces and reaction forces exert equal and opposite force against each other
- action force: you exert force on a chair when you sit down on it because your weight
pushes it down;
- reaction force: the chair exerts a force back on you by pushing up on your body
- forces acting in pairs can have unequal forces
- although action and reaction forces are equal in size, their effects can be very different
- ex: when you drop a ball, gravity is the action force pulling it down; the reaction force pushes
Earth towards the ball but since the amount of force is so small when compared to the size of
Earth, Earth doesn’t move towards the ball.
- ex: when you push off the wall of a pool, your push is the action force; the reaction force
pushes the wall back towards you but the amount of force is so small when compared to the size
of the wall, the wall doesn’t move towards you.
- forces can act in multiple pairs
- multiple forces can act on an object and each force becomes part of a force pair
- ex: when you hit a ball with a bat the following forces come into play:
- bat against ball & ball against the bat
- the person’s hands are exerting a force against the bat & the bat against the player’s
hands
- the person’s bones and muscles in the arm exert a force on the hands & the hands exert a
force on the muscles and bones
Lesson 4 – Gravity and Motion
Essential Question: How do objects move under the influence of gravity?
By the end of this lesson, you should be able to describe the effects that gravity, including Earth’s gravity, has on matter.

- Gravity – a force of attraction between objects due to their mass
- noncontact force that acts between two objects at any distance apart
- gravity pulls things towards the center of Earth but doesn’t push so it’s an attraction force
- gravity depends on a force called weight which depends on the object’s mass
Force = mass x gravity F = mg
- gravity is 9.8m/s 2 on Earth – all objects accelerate the same way on Earth
- if you take away air resistance, all objects fall to the Earth at the same acceleration
- when gravity is the only force acting on two objects, the heavy and light objects reach
the ground at the same time
- heavier objects have more mass and a greater force but take more force to get them to
move – these two forces cancel each other out and causes acceleration to be the same for
all objects
- gravity affects mass equally
- because all master has mass and gravity is a result of mass, all matter is affected by gravity
- every object exerts a gravitational pull on every other object
- when objects aren’t moving towards each other it’s because the gravitational force is too small
or the force of friction holding them in place is larger than the gravitational force
- gravity can cause larger objects, like planets to become round, because all parts of the planet
pull towards the center of mass, making a sphere.
- gravity can act over great distances and cause planets and starts to remain in orbit
- Law of Universal Gravitation – all objects attract each other through gravitational force
- the strength of the force depends on the masses involved and distance between them
- gravitational forces between two objects increases as the distance between their centers
decreases
- objects far apart have a weaker attraction then objects closer together; if the objects
move closer, the attraction increases
- gravitational forces between two objects increases with the mass of each object
- objects with greater mass have more attraction between them
- ex: astronauts on the moon bounce when they walk since the moon has less mass then
Earth so the astronauts weight less when on the moon
- the force of each step the astronaut takes on the moon pushes the astronaut higher
than when he/she is on Earth
- free fall - happens when gravity is pulling an object down and no other forces are acting on it
- orbit - an object is in orbit when it travels around another object in space
- as the one object moves around the other, it’s moving forward but falling towards the object at
the same time
- combination of the forward motion and downward motion due to gravity combine to cause
orbiting

- gravity can make objects move in circles and orbit
- many objects in the universe are in orbit due to gravity: spacecraft, satellites, moon, planets,
comets, meteors, stars, galaxies,
Lesson 5 – Fluids and Pressure
Essential Question: What happens when fluids exert pressure?
By the end of this lesson, you should be able to explain why fluids exert pressure and how the resulting pressure causes motion and the buoyant force.
- fluid - any material that can flow and that takes the shape of its container
- fluids flow because its particles easily move past each other (gas or liquid)
- pressure – measure of how much force is acting on a given area
- any force exerted over an area creates pressure
- ex: when blowing up a balloon, the air in the balloon exerts pressure on the balloon and
increases as more air is added in the balloon
Pressure = force
area
- pascal – metric unit for pressure
- one pascal (1 Pa) is the force of one newton (N) exerted over an area of one square meter
(1 N/m
2
)
- a greater force results in greater pressure
- pressure also depends on the area over which the force is exerted; a bigger area means less
pressure
- the atmosphere has weight because gravity is pulling down on all the gases that make it up
- atmospheric pressure – pressure caused by the weight of the atmosphere
- exerted on everything on Earth
- usually given in kilopascals (kPa)
- As altitude decreases, atmospheric pressure increases; meaning there is less pressure the higher
you get up a mountain and more pressure the lower you go in a canyon.
- gravity pulls water towards Earth’s center
- the weight of the water causes pressure on objects under its surface
- as water depth increase, pressure increases
- when you’re under water, you have the weight of the water putting pressure on you as well as
the weight of the atmosphere above the water putting more weight and pressure on you
- the total pressure under water is the sum of the atmosphere’s pressure and the water above it
- fluids flow from areas of higher pressure to areas of lower pressure

- ex: sucking water up a straw (higher pressure is the water in the cup, lower pressure is the force
exerted by your mouth)
- ex: breathing air into your lungs (higher pressure is the air outside your body, lower pressure is
the expanded lungs)
- ex: wind moves from high pressures centers to low pressure centers
- buoyant force – pressure that a fluid exerts in an upward motion against the bottom of an object that’s
floating in a fluid, like water
-
Archimedes’ principle
– states that the buoyant force acting on an object in a fluid is an upward force
equal to the weight of fluid that the object displaces
- In simple words: when you drop an object into water, the water level rises up the volume of that
object – this is how you get the volume of an irregular object using water displacement
- objects float in a fluid if their weight is equal to the buoyant force
- if the buoyant force pushing up is the same as the force pushing the object down is the
same the object will float within or suspended under the surface of the fluid – they have
the same density so they will float within that liquid
- objects will sink if their weight is greater than the buoyant force – object is more dense than the
liquid it will sink below that liquid
- objects will be buoyed up (float on the top) if the buoyant force working on the objects is greater
than the object’s weight – the object is less dense than the fluid it’s in
- the density of an object is related to its ability to sink or float
Density = mass D = m
volume v
- by increasing or decreasing the mass for volume of an object you can change its density and change the
way it will sink or float
- ex: submarine ballast tanks allow more water to flow into the sub increasing the mass and
making the sub sink in the water; pushing water out of the filled ballast tank will decrease the
mass and make the sub rise in the water
- ex: swim bladder in a fish does the same as the sub’s ballast tanks by changing the volume of
the fish making it float at different depths. Gasses inflate or deflate the swim bladder changing
the volume of the fish.