2. Basic Information: Force: A push or pull on an object Forces can cause an object to: Speed up Slow down Change direction Basically, Forces can cause an object to … Accelerate!

3. Forces can act as: 1.Contact Forces 2.Field Forces Forces are vectors Have magnitude and direction Units: Newtons

4. Force of Gravity (F g ) aka Weight (W) Definition: force of attraction acting between objects Always acts in the downward direction Normal Force (F N ) Definition: Force exerted by the surface on the object Always acts perpendicular to the surface Applied Force (F A ) Definition: Force applied by a person or object Can be in any direction

5. Friction Force (F f ) Definition: force that resists motion caused by the surfaces of objects in contact with each other Always acts in the opposite direction of the moving object Tension Force (F T ) Definition: force applied by rope or cable on an object Can act in any direction Net Force (F Net ) Definition: The sum of all forces acting on an object Can act in any direction

6. Newton’s 1 st Law of Motion Every object will persist in its state of rest or in its state of uniform motion (constant velocity) in a straight line unless it is acted upon by an external force Summary: An object at rest stays at rest. An object in motion stays in motion unless a net force acts on it Also known as the law of inertia More mass = more inertia

7. At rest: with no force Stays at rest Unless an external force acts on it

8. In motion: Stays in Motion: Unless an external force acts on it

9. Newton’s 2nd Law of Motion When a force is applied, the mass accelerates. Force = mass x acceleration Relationship: Force and Acceleration = direct relationship Mass and Acceleration = inverse relationship

10. More Force = More Acceleration More Mass = Less Acceleration

11. Newton’s 3 rd Law of motion For every action, there is an equal and opposite reaction All forces come in pairs According to Newton, whenever objects A and B interact with each other, they exert forces upon each other. When you sit in your chair, your body exerts a downward force on the chair and the chair exerts an upward force on your body. There are two forces resulting from this interaction - a force on the chair and a force on your body.

12. All materials have some degree of roughness. This roughness creates bumps and valleys on the surfaces of the materials. This roughness creates friction.

13. Friction causes an object to slow down and come to a stop. Friction always acts in opposite direction of the moving object.

14. Friction Static FrictionKinetic Friction Friction when the object is stationary The type of friction with the greatest amount of force Friction when the object is moving Rolling Friction Sliding Friction

15. The amount of friction is dependent upon: The types of surfaces in contact The force between the object and surface Friction Formula: F f =  F N Variables: F f  Friction force  : coefficient of friction F N : Normal Force

16. Mass is the amount of matter in an object. An object’s mass does not change. Weight is based on the object’s mass and the acceleration due to gravity at that location. If the acceleration due to gravity changes, then the weight changes. The acceleration due to gravity on Earth is -9.81 m/s 2. The acceleration due to gravity on the moon is -1.67 m/s 2. Therefore, the object will weigh more on the Earth than on the moon. Gravity is a force of attraction between objects. All objects have a gravitational force. The force of gravity is found using the formula: F g = mass x acceleration due to gravity

17. Free Body Diagrams A simple sketch used to show all the forces that are acting on an object. Draw a quick sketch of the object. Often a box will do just fine. For every force acting on it, draw a vector arrow Label each arrow with the appropriate forces A person pushes a box to the right across the floor. Draw a free-body diagram.

18. A 24.0 kg mentos and coke bottle rocket exerts 350.0 N of force in being shot upward. What’s the rocket’s acceleration?

19. A 1682 kg car accelerates across the level street at 2.45 m/s 2. If the engine applies 5250 N of force to the road, what is the friction force? What is the coefficient of friction?