FORCES
Contact
vs.
Noncontact
OBJECTIVES
 Distinguish between contact and noncontact forces.
 Explore the Law of Gravity by recognizing that every
object exerts a gravitational force.
ESSENTIAL QUESTION
 What forces may hinder the motion of a soccer ball
rolling across a field?
AGENDA
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Bell Ringer
PowerPoint with Notes
Brain Pop with Review Quiz: Gravity
Check for Understandings
Mini Book Activity
Independent Practice
FORCE: A PUSH OR PULL
Contact Force
 A force that can cause
or change motion of an
object by touching it.
Motors and gears
operate through contact
forces.
Contact Force Examples:
• Friction
• Normal Force
• Air Resistance
• Applied Force
Non-Contact Force
 Force that results when
the two objects are not
in physical contact with
each other, yet are able
to exert a push or pull.
Non-Contact Force Examples:
• Gravitational Force
• Electrical Force
• Magnetic Force
CONTACT FORCES
 Applied Force: A force typical push or pull, pushing a door
open, pulling a rope.
 Friction: Happens when two objects rub against each other.
Friction opposes motion.
 Normal Force: The normal force is the support force exerted
upon an object that is in contact with another stable object.
For example, if a book is resting upon a surface, then the
surface is exer ting an upward force upon the book in order to
suppor t the weight of the book .
 Air Resistance: The air resistance is a type of frictional force
that acts upon objects as they travel through the air.
CONTACT FORCES
Normal Force= 10N
NON-CONTACT FORCES
 Magnetic Force: A kind of non contact force, materials such as
iron, nickel, cobalt and other magnets just need to be near
the magnet to be attracted or repelled.
 Electric Force: Noncontact force of electrical charges.
 Gravitational Force: The force of attraction between any two
objects in the universe. All objects have gravitational force.
The mass of an object and its distance determines the
strength of its gravitational force.
GRAVITY
Mass and distance affect the force of
gravity. The greater the mass and the
closer the object, the stronger its
gravitational pull.
GRAVITY
How does the force of gravity change
as the mass of objects and distance
between them changes?
The force of gravity between
two objects depends on two
factors:
 Mass
 Distance
*Longer arrows represent a greater force of gravity.
MASS VS. WEIGHT
 The amount of matter in
an object.
 Unit: Grams
 Does not depend of
gravity.
 Measured with a triple
beam or digital balance.
 Measure of the Earth’s
gravitational pull (a
force).
 measured in lbs. or N
 Changes depending on
the gravitational force.
 Measured using a
spring scale.
BRAIN POP: GRAVITY
Quiz Afterwards!
CLASSIFY THE FORCES
A foot kicking a soccer ball
An apple falling off a tree
A paper clip sliding towards a magnet
A bat striking a baseball
Two magnets pushing apart from one
another
The moon orbiting the Earth
A compass needle turning North
A hand pushing an object
Shoes rubbing against the floor
DISCUSS!
Now that we have learned about forces, lets
talk about the essential question! You will
answer the EQ on the front of your foldable.
ESSENTIAL QUESTION
What forces may hinder the motion of a soccer
ball rolling across a field?
Make a Book!
Time to tap into some creativity!
You will create a 6-page book that
covers what you learned today.
(10 minutes)
Front Cover: “Force: A Push or Pull”
Your name and the period.
Page 1: Contact Force
Page 2: Examples
Page 3: Non Contact Force
Page 4: Examples
Page 5: Gravity
Page 6: Summary
INDEPENDENT PRACTICE