Chapter 23: Newton's Laws of Motion

Goals
■ Describe how to create
balanced and unbalanced
forces on an
object.
■ Demonstrate forces
that change the speed
and the direction of an
object’s motion.
Possible Materials
block
book
pieces of string (2)
spring scales (2)
Safety Precautions
706 CHAPTER 23 Newton’s Laws of Motion
IT Stock International/Index Stock/PictureQuest
Design Your Own
Bayanced and
Unbalanced Forces
Real-World Question
Newton’s laws tell you that to change the velocity
of an object, there must be an unbalanced
force acting on the object. Changing the
velocity can involve changing the speed of
the object, changing the direction of motion,
or changing both. How can you apply an
unbalanced force to an object? How does the
motion change when you exert a force in
different ways?
Form a Hypothesis
Predict how the motion of a block will change
when different forces are applied to it. Consider
both speed and direction.
Test Your Hypothesis
Make a Plan
1. Describe how you are going to exert forces on the block using the
available materials.
2. List several different ways to exert forces or combinations of forces
on the block. Think about how strong each force will need to be to
change the motion of the block. Include at least one force or combination
of forces that you think will not change the object’s motion.
3. Predict which forces will change the object’s direction, its speed,
both, or neither. Are the forces balanced or unbalanced?
Check Your Plan
1. Make sure that your teacher approves your plans before going any
further.
2. Compare your plans for exerting forces with those of others in
your class. Discuss why each of you chose the forces you chose.