a. When an object pushes or pulls on another object, the first object exerts a FORCE on the second object b. Force is described by the strength and direction in which the object acts c. Force is measured in Newtons I. FORCE BASICS

a. Two main groups i. Contact forces ii. Forces that act at a distance b. Three Contact Forces i. Applied force: one object putting on a force onto another object 1. example: if you open a door, you are applying a force to the door 2. Applied forces often change the motion and direction of the second object ii. Normal force: this is the force between two objects 1. This force acts in a perpendicular fashion to the object iii. Friction: when two surfaces exert a force on each other 1. This force acts opposite of the object II. MAIN TYPES OF FORCES

c. Forces acting at a distance i. Electrical forces: force between two charged objects 1. Opposites attract i. I rub a balloon on my head and my hair sticks to it. If my hair is positively charged, what charge does the balloon have? ii. Magnetic Force 1. All magnets have a north and a south magnetic pole 2. These opposites attract each other 3. Like poles will repel each other i. If I bring a North magnet close to a north magnet what will happen? II. MAIN TYPES OF FORCES

iii. Gravitational force: follows the Law of Gravity and the Law of Universal Gravitation 1. Law of Gravity: What goes up must come down a. This also says that objects will be pulled straight down 2. Law of Universal Gravitation: The force of gravity acts between all objects in the universe that have mass. 3. Factors of Gravity a. Mass: the more mass the more gravitational pull between it and other objects b. Distance: As distance increases gravitation pull decreases 4. How are weight and mass different? II. MAIN TYPES OF FORCES

1.) Open a book to pages On a piece of notebook paper, go through the book and write the definitions of the highlighted words. Answer the following questions in complete and detailed sentences 2.) What happens to the gravitational pull as the distance between two objects increases? 3.) If the moon and earth are both exerting a gravitational force on you, give 2-3 reasons why you stay on the earth as opposed to floating up to the moon. 4.) Look at figure 5 on page 334, which object in the outside orbit will have the greatest gravitational pull toward the sun and why? 5.) On page 335 of your book, read the box titled “Weight and Mass” then answer the question asked under “Figure 6” 6.) What force keeps you from falling through the bed when you sleep on it? 7.) What is the difference between a Normal Force and an Applied Force? IN CLASSWORK 10/15

a.When showing force we use arrows that point in the direction of the force i. The bigger the arrow the stronger the force ii. Example : III. BALANCED AND UNBALANCED FORCES

b. If the forces acting on an object are balanced the object will not move c.If the forces acting on an object are unbalanced the object will move d.Net Force: the combination of all the forces acting on an object i. This determines how an object will accelerate ii. Example Problems III. BALANCED AND UNBALANCED FORCES

a.Newton’s First law of Motion: b.Inertia: An objects resistance to change in motion i. Example: When your car stops moving suddenly, what happens to you? You keep moving forward in the seat until the seat belt catches you 1. This is because of inertia, your body wants to keep moving even though the car has stopped ii. Inertia and mass relationship 1. The greater the mass the greater the inertia 2. The greater the inertia and mass, the greater the force needed to change the objects motion IV. NEWTON’S LAWS OF MOTION

c. Newton’s Second Law of Motion: An objects acceleration depends on its mass i. If you increase the force on an object, but the mass has not changed, the acceleration will increase ii. If you increase the mass on an object, but the force does not change, the acceleration will decrease. iii. Equation IV. NEWTON’S LAWS OF MOTION

1.) If a 100 N net force acts on a 50 kg car, what will the acceleration be? 2.) If this same car moves downward at an acceleration of 9.8 m/s 2, what is the Force on the car? IV. NEWTON’S LAWS OF MOTION