Lesson 3: Effects of Forces

Lesson 3 - Effects of Forces

Net Force

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The net force is found by combining all
forces on an object.

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If the forces on an object act in the same

direction, the strengths of the forces are
added.

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If forces act in opposite directions, the

strengths of the forces are subtracted.

Example 1

Match

Match the following

24N Right

12N Left

0N (No Direction)

• 24N Right

• 12N Left

• 0N (No Direction)

Newton’s 1st Law: Balanced and Unbalanced Forces

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Balanced forces are forces that have a net force equal to 0.

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Unbalanced forces are forces that result in a net force not equal to 0.

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Unbalanced forces cause a change in motion.

=

Opposite forces that are equal cancel
each other out to equal a 0 net force.

=

Opposite forces that are unequal don’t

cancel and result in motion.

Example 2

Newton’s 1st Law

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Newton’s first law of motion is also
known as the Law of Inertia.

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An object at rest stays at rest if the
forces are balanced.

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An object in motion will stay in
motion (same speed/direction) if the
forces are balanced.

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If the object is acted upon by an
unbalanced outside force, it’s
motion will change.

Always wear your
seatbelt!

Open the assignment “Lesson

3 PhET Simulation

Questions”. You will be using

the PhET simulator in the

NearPod to answer questions

for this assignment.

Multiple Choice

Which of the following is an example of Newton's First Law of Motion?

• You fall on the ground and the ground pushes back

• A comet flies through space at a high speeds until Gravity pulls on it

• A larger mass requires more force to move

Newton’s 2nd Law of Motion

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Newton’s second law of motion states
that an object’s acceleration depends
on the mass and the force acting on
the object.

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A larger net force will result in a larger
acceleration.

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A larger mass will result in a smaller
acceleration.

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The equation for Newton's second law is

F= m x a

Example 3

Force = Mass x Acceleration
Mass = Force / Acceleration
Acceleration = Force / Mass

Example: A 5 kg object
accelerates at 2 m/s2. What force
was used?

F = m x a = 5 kg x 2 m/s2

F = 10 N

Draw

Apply Newton's 2nd Law to the picture. Draw a force arrow for each person to show the amount of force required if both objects were to have the same acceleration. (Hint: Think about how mass effects the amount of force needed to move an object)

Forces Around You

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Friction is a force that opposes motion
between two surfaces that are touching

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Friction slows an object's velocity down

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Friction can be helpful or harmful
depending on the situation
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Ex: Friction help you stop when sliding
into the base