1. EQ: What causes an object’s motion to change?
Engage
EQ: What causes an object’s motion to change?

2. Forces On And Motions of Objects
Description: you will change the motion of a rolling ball by applying forces.
Materials:
Activity sheet
Ball
Forces On And Motions of Objects

3. Find your table’s area out in the hall and sit in a small circle leaving enough space to roll a ball a short distance.
Apply just enough force to get the ball rolling.
Once it is rolling, have the closest group member apply a force with his/her hand so that the ball starts to roll faster.
Record your observations on your data table
Repeat step 2
Once it is rolling, have the closest group member apply a force as directed under the “Change of Motion” column
Record your observations for each change on your data table
Return to the room
Collaboratively answer questions 1-3
Procedures

4. EQ: What causes an object’s motion to change?
Forces
EQ: What causes an object’s motion to change?

5. A hard kick sends a soccer ball shooting down the field toward a goal.
Just in time, the goalie leaps forward, stops the ball, and quickly kicks it in the opposite direction.
In a soccer game, the ball is rarely still.
Why?
What causes an object to start moving, stop moving or change direction?

6. Forces The answer is force.
Scientifically, a force is a push or a pull.
When an object pushes or pulls on another object, the first object exerts a force on the second object
Forces

7. The first object exerts a force on the second object.
Which object is exerting the force?
On which object is the force being exerted?
The first object exerts a force on the second object.

8. The first object exerts a force on the second object.
Which object is exerting the force?
On which object is the force being exerted?
The first object exerts a force on the second object.

9. Force is described by its strength and in the direction it moves.
The strength of a force is measured in newtons (N)
You exert about one newton of force when you lift and small lemon.
1N=lifting a small lemon
Measuring force

10. The direction and strength of a force can be represented by an arrow.
The arrow points in the direction of the force.
First object points to the second object
Object 1(F1) Object 2(F2)
The length tells you the strength of the force
The longer the arrow, the stronger the force
Measuring Force

11. Measuring Force In which direction is the force being exerted?
What is the strength of the force?
Measuring Force

12. Often, more than a single force acts on an object at one time.
The combination of all forces acting on an object is called the net force.
The net force determines:
if an object moves
and in which direction it moves.
Combining Forces

13. Force 1 (N) +Force 2 (N) ____________ Total Force (N) Combining Forces
When forces act in the same direction, the net force can be found by adding the strengths of the individual forces.
Force 1 (N)
+Force 2 (N)
____________
Total Force (N)
Combining Forces

14. When forces act in opposite directions, they also combine to produce a net force.
But you must pay attention to the directions of the forces.
Combining Forces

15. Adding a force in one direction to a force in the opposite direction is trickier.
It is treated like adding a positive number to a negative number.
When two forces act in opposite directions, they combine by subtraction.
Combining Forces

16. The force ALWAYS acts in the direction of the greater (larger, bigger
The force ALWAYS acts in the direction of the greater (larger, bigger..) force.
Combining Forces

17. If the opposing forces are of equal strength, then there is NO net force.
They cancel each other out.
There is no change in the object’s motion.
Combining Forces

18. Types of Forces Contact Forces Normal (balanced) Friction Tension
At a Distance Forces
Normal (balanced)
Friction
Tension
Fluid
Air resistance
Applied
Spring
Gravitational
Electrical
Magnetic
Types of Forces

19. Types of Forces Unbalanced Balanced
When there is a net force acting on an object.
Can cause an object to start moving, stop moving, or change direction.
Unbalanced forces acting on an object result in a net force and cause change in the object’s motion
Equal forces acting on an object in the opposite direction.
Balanced forces acting on an object do not change the direction of the object’s motion.
Types of Forces

20. Summarizing AP Write a summary of forces
What are forces?
How are they measured?
How are they combined?
What are the two types of forces?
Compare your summary with your partner(s)
Summarizing AP