Transcript Unit 7 Lesson 1

Unit 7 Lesson 1 What Are Forces?
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Unit 7 Lesson 1 What Are Forces?
Florida Benchmarks
• SC.5.P.13.1 Identify familiar forces that cause
objects to move, such as pushes or pulls,
including gravity acting on falling objects.
• SC.5.P.13.2 Investigate and describe that the
greater the force applied to it, the greater the
change in motion of a given object.
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Unit 7 Lesson 1 What Are Forces?
Florida Benchmarks
• SC.5.P.13.3 Investigate and describe that the
more mass an object has, the less effect a given
force will have on the object’s motion.
• SC.5.P.13.4 Investigate and explain that when a
force is applied to an object but does not move, it
is because another opposing force is being applied
by something in the environment so that the
forces are balanced.
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Unit 7 Lesson 1 What Are Forces?
Pushing and Pulling
• A force is a push or pull.
• Forces can change the movement of an object.
• Forces can change the shape of an object.
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Unit 7 Lesson 1 What Are Forces?
Pushing and Pulling
• Weight is a measure of the force gravity exerts on
an object.
• Spring scales are used to measure force in units
called newtons (N).
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Unit 7 Lesson 1 What Are Forces?
Two Common Forces
Gravity
• Gravity is a force of attraction between two
objects. It acts even when objects are not
touching.
• The size of the force increases as the mass of the
objects increases.
• The size of the force decreases as the distance
between the objects increases.
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Unit 7 Lesson 1 What Are Forces?
Friction
• Friction is a force that opposes motion.
• Friction acts between objects that are touching.
• Friction produces thermal energy.
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Unit 7 Lesson 1 What Are Forces?
Balanced or Unbalanced?
• Balanced forces are forces on an object that are
equal in size and direction.
• Unbalanced forces are forces that cause a
change in motion.
• A force must overcome the force of friction before
an object will move.
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Unit 7 Lesson 1 What Are Forces?
Push (or Pull) Harder!
• Large forces can cause objects to change velocity,
or accelerate, quickly.
• Changes in velocity include changes in speed and
changes in direction.
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Unit 7 Lesson 1 What Are Forces?
Pull (or Push) Harder!
• What should the boy do differently to make the
bell ring?
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Unit 7 Lesson 1 What Are Forces?
I’m Not Moving!
• If the same force is applied, objects with greater
mass accelerate slower than objects with less
mass.
• How can the steel ball be made to go higher?
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Unit 7 Lesson 1 What Are Forces?
I’m Not Moving!
• The larger the force applied to an object, the
greater the acceleration is.
• The less an object’s mass is, the less force is
needed to change its motion.
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Unit 7 Lesson 1 What Are Forces?
I’m Not Moving!
• Why does it take the full truck longer to stop than
the empty truck?
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Unit 7 Lesson 1 What Are Forces?
Let’s Go to Mars!
• Unbalanced forces can allow rockets to oppose
Earth’s gravity.
• Small booster rockets can change the direction of
the vehicle’s motion.
• Rockets reach an “escape velocity” at which
Earth’s gravity will no longer pull the vehicle back
down.
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Unit 7 Lesson 1 What Are Forces?
Let’s Go to Mars!
• Balanced forces allow a spacecraft to move in one
direction at a constant velocity through space.
• Once the spacecraft reaches Mars, it will
accelerate toward the surface because of gravity.
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