Review How do we know when an object is in motion? When its distance from another object is changing
Review What do we use to measure motion? Speed Velocity Acceleration
Today’s Goals… I can describe how forces affect motion. I can explain the difference between balanced and unbalanced forces.
Activity! Take everything off of your desk Using the materials at your table, you and your partner are going to investigate and create different methods for moving the block across the table
What did you learn from the activity? What was required to make the block move? A push or a pull Did the block move when there was no push or pull? When you pushed or pulled the block it was set in motion!
What is a force? A force is a push or a pull When one object pushes or pulls another object you can say that the first object is exerting a force on the second object! For example: You exerted a force on the blocks when you made them move You exert a force on your pencil when you write You exert a force on a rock when you throw it
What is a force? Forces can be described by how strong they are AND in what direction When you pushed the book you exerted a force in a different direction than when you pulled the book! Some of the forces you exerted on the books may have been stronger than others!
What is a force? Forces are measured with a spring scale The units for forces are newtons (N)
Unbalanced Forces Imagine that you need to push a heavy desk across the floor When you push on the desk you are exerting a force If a friend helps you, then the total force exerted on the desk is your force plus your friend’s force!
Unbalanced Forces When two forces act in the same direction you add them together =
Unbalanced Forces When two forces act in opposite directions they combine by subtraction If one force is greater than the other, then the overall force is in the direction of the greater force =
Unbalanced Forces The overall force is sometimes called the net force When there is a net force acting on an object, then the forces are said to be unbalanced Unbalanced forces acting on an object will change an object’s motion
Balanced Forces Forces exerted on an object do not always change an object’s motion or cause it to move balanced forces are equal forces acting on an object in opposite directions
Balanced Forces One force is exactly balanced by the other Balanced forces acting on an object will not change the object’s motion When you add equal forces exerted in opposite directions the net force = 0=
Revisiting today’s goals… I can describe how forces affect motion. I can explain the difference between balanced and unbalanced forces.
Assignment! Choose an activity (it could be a sport or a hobby) and describe all the forces in it that can cause motion.