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Unit 4 Lesson 3 Newton’s Laws of Motion
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Unit 4 Lesson 3 Newton’s Laws of Motion
Genius at Work
How did Sir Isaac Newton contribute to
scientific thought?
• Newton was a English natural philosopher whose
work on gravity led him to develop the three laws
of motion.
• Newton’s laws of motion describe the
relationships between forces, matter, and motion.
• These laws were published in the late 1600s in a
set of books known as the Principia.
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Unit 4 Lesson 3 Newton’s Laws of Motion
How did Sir Isaac Newton contribute to
scientific thought?
• In the Principia, Newton set forth a scientific
method that revolutionized how scientists
conducted investigations.
• In addition to inventing the reflecting telescope,
Newton also heavily influenced modern astronomy
and mechanical engineering.
• The impact of his research continues even in
modern times.
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Unit 4 Lesson 3 Newton’s Laws of Motion
To Move or Not to Move
What is Newton’s law of inertia?
• Newton was a English natural philosopher whose
work on gravity led him to develop the three laws
of motion.
• Inertia is the tendency of an object to resist a
change in motion.
• Unbalanced forces always change the motion of
an object because the net force on the object is
not zero.
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Unit 4 Lesson 3 Newton’s Laws of Motion
What is Newton’s law of inertia?
• An object at rest stays at rest when balanced
forces cancel each other out for a net force of
zero.
• An object in motion stays in motion until an
unbalanced force is applied.
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Unit 4 Lesson 3 Newton’s Laws of Motion
Why does friction affect motion?
• Friction is a force that opposes motion between
objects that are touching.
• Because of friction, an object rarely maintains
constant motion.
• Friction is an important unbalanced force, since it
make everyday actions like walking possible.
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Unit 4 Lesson 3 Newton’s Laws of Motion
How is the law of inertia applied to
everyday situations?
• Inertia is the property of matter that causes a
moving object to keep moving and a stationary
object to remain in place.
• You experience this property when trying to stop
on a slippery surface.
• Automobile safety devices and testing takes the
effects of inertia into account.
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Unit 4 Lesson 3 Newton’s Laws of Motion
Pushing Forward
What is Newton’s law of force and
acceleration?
• Newton’s second law of motion states that the
acceleration depends on the mass of the object
and the net force involved.
• Acceleration is the rate at which velocity
changes over time.
• Newton developed a way to describe the
mathematical relationship among force, mass, and
acceleration.
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Unit 4 Lesson 3 Newton’s Laws of Motion
What is Newton’s law of force and
acceleration?
• An object accelerates in the direction of the net
force.
• Acceleration can be calculated using the following
equation: F = ma
• F represents force, m represents mass, and a
represents acceleration. Remember that you can
rearrange the equation to find the unknown
quantity (i.e. a = F/m).
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Unit 4 Lesson 3 Newton’s Laws of Motion
How is the law of force and
acceleration applied to everyday
situations?
• This law indicates that an object with greater
mass requires a greater force to accelerate the
object.
• Engineers use the law of force and acceleration
when they design engines for vehicles and
construction equipment.
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Unit 4 Lesson 3 Newton’s Laws of Motion
Action and Reaction
What is Newton’s law of actionreaction?
• Newton’s third law of motion states whenever one
object applies a force on a second object, the
second object applies an equal and opposite force
on the first object.
• The force exerted by the first object is called the
action force
• The force exerted by the second object is called
the reaction force.
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Unit 4 Lesson 3 Newton’s Laws of Motion
What is Newton’s law of actionreaction?
• The third law of motion can be restated this way:
All forces act in pairs.
• Action and reaction forces do not act on the same
object.
• The forces are equal but act on different objects
and in different directions.
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Unit 4 Lesson 3 Newton’s Laws of Motion
How is the law of action-reaction
applied to everyday situations?
• Gravity is a force of attraction between objects
due to their masses.
• Earth exerts an action force on us and countless
objects, but the reaction force is hard to detect
because Earth is so massive.
• Whenever you exert a force on an object, it
pushes or pulls on you.
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