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

2. 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?

3. 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

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

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

6. Measuring force 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

7. Measuring Force 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

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

9. Combining Forces 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.

10. 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)

11. Combining Forces 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.

12. Combining Forces 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.

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

14. Combining Forces 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.

15. Types of Forces UnbalancedBalanced 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.

16. 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)

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