Unit 7 Lesson 1 What Are Forces?
Copyright © Houghton Mifflin Harcourt Publishing Company
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.
Copyright © Houghton Mifflin Harcourt Publishing Company
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.
Copyright © Houghton Mifflin Harcourt Publishing Company
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.
Copyright © Houghton Mifflin Harcourt Publishing Company
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).
Copyright © Houghton Mifflin Harcourt Publishing Company
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.
Copyright © Houghton Mifflin Harcourt Publishing Company
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.
Copyright © Houghton Mifflin Harcourt Publishing Company
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.
Copyright © Houghton Mifflin Harcourt Publishing Company
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.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 7 Lesson 1 What Are Forces?
Pull (or Push) Harder!
• What should the boy do differently to make the
bell ring?
Copyright © Houghton Mifflin Harcourt Publishing Company
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?
Copyright © Houghton Mifflin Harcourt Publishing Company
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.
Copyright © Houghton Mifflin Harcourt Publishing Company
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?
Copyright © Houghton Mifflin Harcourt Publishing Company
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.
Copyright © Houghton Mifflin Harcourt Publishing Company
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.
Copyright © Houghton Mifflin Harcourt Publishing Company