FORCES AND MOTION
Table of Contents
Forces ……...…….……………………………3 Motion…………………………………………4 Gravity………….…………………………...…5 Changing Motion…….………………...……6 Illustrating Motion…………………….……7 Glossary………………………………………8
T H I S B O O K B E L O N G S T O :
__________________
© Cheryl Gore 2013
Forces and Motion Page 2
By the end of this unit, you should be able to answer…
• What is the origin of motion?
• How are motion and gravity connected?
• What is gravity? How does gravity “work?”
• How are force and motion connected? How can we describe this relationship?
• How can we model the relationship of position, motion, direction and speed?
© Cheryl Gore 2013
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Forces
Forces Change Things
What Affects Force
Think and Answer
In what two ways can a force be applied?
Examples of Balanced and Unbalanced Forces
Examples of Push and Pull
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Motion
Connecting Motion and Force
Connecting Motion and Gravity
Think and Answer
Define motion in your own words? Give a variety of real life examples of motion.
Connecting Motion and Mass
Connecting Motion and Friction
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Forces and Motion Page 5
Gravity
Think and Answer
Why is the gravitational pull so different between an object on Earth and an object on the moon?
Gravity Near and Far
Illustrating Gravity
How Gravity Works
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Changing Motion
Examples of Changing Motion Due to Force
Calculating Speed
Examples of Changing Motion Due to Mass
Think and Answer
How can changing the mass effect the force needed to change an object’s motion?
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Illustrating Motion
Think and Answer
How can a graph show a relationship between distance and time in regards to motion?
Constant Motion
No Motion
Reading Graphs
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axis balanced force
distance elapsed time
force friction
gravity mass
motion position
time unbalanced force
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Glossary
© Cheryl Gore 2013
FORCES AND MOTION
Table of Contents
Forces ……...…….……………………………3 Motion…………………………………………4 Gravity………….…………………………...…5 Changing Motion…….………………...……6 Illustrating Motion…………………….……7 Glossary………………………………………8
T H I S B O O K B E L O N G S T O :
__________________
© Cheryl Gore 2013
Forces and Motion Page 2
By the end of this unit, you should be able to answer…
• What is the origin of motion? The origin of motion is the starting point of an object. It could be the starting line in a race or the car in the driveway before going to the store. However, for motion to begin a force must be applied to it.
• How are motion and gravity connected? The Sun’s gravitational pull keeps our planet orbiting the Sun. The motion of the Moon is affected by the gravity of the Sun and the Earth. The Moon’s gravity pulls on the Earth and makes the tides rise and fall every day.
• What is gravity? How does gravity “work?” Gravity is a force of attraction between two objects. Gravity acts like a magnet that pulls objects together. Gravity on Earth holds everything close to the planet.
• How are force and motion connected? How can we describe this relationship? For an object to be in motion, a force must be applied to it. The amount of force and direction of the force results in the amount of motion and direction of the object. Force and motion are directly related.
• How can we model the relationship of position, motion, direction and speed? We could use/analyze a graph or coordinate grid to show position, motion, direction and speed. We could calculate speed by finding the difference of the starting and ending position (distance) and dividing it by the time.
© Cheryl Gore 2013
Forces and Motion Page 3
Forces
Forces Change Things
• Forces change speed • Forces can change direction of motion. • The greater the force, the greater the change
in motion. • Forces can stop an object from moving.
What Affects Force
Mass: The greater the mass, the more force needed to move the object. Less mass, means less force to move an object. Distance: The greater the force needed to move an object a further distance.
Think and Answer
How can all forces be grouped? All forces can be grouped as a push or a pull. Even gravity is considered a pull of attraction.
Examples of Balanced and Unbalanced Forces
BALANCED: Book on desk, shirt on hanger, fork on plate, chairs stacked UNBALANCED: Kicking a soccer ball, swinging on swing, picking up a fork, walking
Examples of Push and Pull
PULL: zipping up a zipper on a jacket, opening a door, putting on book bag
PUSH: bouncing a ball, walking a stroller/cart, eating food (pushing your teeth together)
© Cheryl Gore 2013
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Motion
Connecting Motion and Force
For an object to move or have motion a force (push or pull) must act on the object.
The more force added to an object the more motion the object will encounter.
For an object to continually move, a force must continually be applied to it.
The direction of the force can change the direction and speed of the object’s motion.
Connecting Motion and Gravity
Gravity is the force of attraction between two objects. The force of attraction is greater between larger objects.
Think and Answer
Define motion in your own words? Give a variety of real life examples of motion. Motion is an object that is moving. Real life examples of motion are: pencils writing, mouths talking, feet kicking, leaves blowing in the wind, acorn falling, and playing basketball.
Connecting Motion and Mass
The more mass of an object the more force needed to move the object or to keep it in motion. If two objects of different mass have the same amount of force applied, the object with less mass will go further. The object with more mass will require more force to stop its motion.
Connecting Motion and Friction
Force, such as friction, can stop the object’s motion. It is when two objects rub in opposite directions.
The grass slows/stops a rolling ball, tires put friction on the road to make a car go and stop.
© Cheryl Gore 2013
Forces and Motion Page 5
Gravity
Think and Answer
Why is the gravitational pull so different between an object on the earth and an object on the moon? The moon is much smaller. The pull between the moon and a person is less than the pull of Earth and that same person.
Gravity Near and Far
The pull of gravity is stronger when the two objects are closer. The pull of gravity is strong when an object is larger. Because the Earth is so large, the gravitational pull between all other objects and Earth is strongest. All objects, no matter their mass, will fall to the Earth at the same rate, air resistance may change this.
Illustrating Gravity
weaker stronger
The gravitational pull between the sun and Earth is stronger than that of Earth and moon because the sun is so much larger.
How Gravity Works
Gravity is what pulls you down to when you jump. Gravity is a force that attracts all objects to all other objects. It acts on all objects and is affected by mass and distance. (The greater the mass the greater the attraction and the greater the distance the less the attraction.) The force of gravity acting on an object is the object’s weight.
© Cheryl Gore 2013
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Changing Motion
Examples of Changing Motion Due to Force
• A car speeds up when you press the gas pedal • A pencil rolls of the desk and falls to the ground due to
gravity • A ball bounces back after being thrown to a wall • A bicycle stopping because the tires slow on the street • A walker goes slower because they are tired • A sled goes faster because it goes down a larger hill • A baseball goes into outfield after being hit by a bat
Calculating Speed
Speed is distance divided by time.
Speed = Distance Time
35 miles per hour 20 centimeters per millisecond 8 feet per second 150 meters per minute
Examples of Changing Motion Due to Mass
• Running with your book bag on or off to catch the bus • Pulling a wagon full of kids or an empty wagon • Playing with football safety equipment on versus no equipment • Carrying wet clothes or carrying dry clothes • Pushing a two door sedan or pushing a SUV
Think and Answer
How does the mass and force applied affect the motion of an object? The more mass in an object, the more force needed to move/stop it. If two objects of the same mass are in motion the one with the greater force will go further. If two objects of different mass use the same amount of force the object with less mass will go further.
© Cheryl Gore 2013
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Illustrating Motion
Think and Answer
How do the graphs show the relationship between distance and time? The distance is on the y axis and time on the x axis. If you take total distance and divide it by total time you can find the average speed. You can also see the motion of the object at varying times.
Constant Motion
With the graph on the right, the tallest line covered the most distance in the shortest amount of time. They both moved at a constant motion; which means an equal force was applied the entire time to each of the two objects. Amount of force isn’t shown.
No Motion
d i s t a n c e T i m e
Reading Graphs
All Bicyclists start at the same starting point. Bicyclist R: starts out at the fastest speed, stops after 15 minutes for about 2-25 minutes and then speeds up quickly.
Bicyclist S: starts out at the slowest pace, then picks up speed at the end. Bicyclist T: starts out at a constant speed and then slows down at the very end.
Bicyclist U: Has a constant rate the entire race.
© Cheryl Gore 2013
axis: a reference line on a graph or coordinate grid
balanced force: forces that cancel each other out when acting together on a single object
distance: the extent or amount of space between two things, points or lines
elapsed time: the time that elapses or passes while an event is occurring
force: a push or pull exerted by one object on another, causing a change in motion
friction: a force that opposes the motion of one object moving past another
gravity: the force of attraction between any two objects due to their mass
mass: a measure of the amount of matter in an object
motion: the manner in which an object moves
position: the location of an object in space
time: measuring duration, could be in days, hours, minutes, milliseconds or more
unbalanced force: forces that do not cancel each other out when acting together on a single object
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Glossary
© Cheryl Gore 2013
