Chapter 11 Section 3 Physical Science (Freshman Physics)

 1. Define force  2. Explain the four fundamental forces  3. Describe the types of friction  4. Be able to state Newton’s first law of motion  5. Define inertia

 Force is defined as any action that can change the state of motion of an object Forces can act through contact or at a distance

 There are four fundamental forces in nature: 1. Gravity – by far the weakest 2. Electromagnetic – Electricity and light 3. Weak nuclear – Keep electrons in motion 4. Strong nuclear – Holds protons and neutrons together in the nucleus (Strongest)

 Forces that result from a push or a pull. Objects are in contact with each other ~ hence the name contact forces.  Examples:  you catch a ball it stops  moving  You push a cart it starts moving

 Do not require objects to be touching each other.  These forces can cause objects to move.  Examples:  gravity  magnets

 When two forces act equally and opposite, they cancel out.  NO NET FORCE

 Unbalanced forces do not cancel completely.  The net force is greater than zero.

 The force of friction always opposes the motion.  It is always in the opposite direction of motion.

 The friction that occurs between two things that are stationary.  Is greater than Kinetic friction.

 The force that opposes the movement of two surfaces that are in contact and are moving over each other.

 Sliding Friction – Objects are sliding  Rolling Friction – Objects are rolling

 Friction can be harmful or useful

First Semester

 British scientist and mathematician  One of the most prolific scientists in history

1492 Christopher Columbus stumbles upon an already “discovered” America Isaac Newton Gameboy first used in 1988

 Without an external force acting on it, an object in motion will continue in motion.  “An object at rest remains at rest and an object in motion maintains its velocity unless it experiences a net force  Also known as “the law of Inertia”

An object will just sit there… Unless… A force is applied

 The tendency of an object to resist a change in motion unless an outside force acts on the object.  All objects resist change in motion, so all objects have inertia.

Objects with greater mass have greater inertia. Less Inertia More Inertia

 When you travel in a car you have inertia.  When the car brakes, turns or accelerates, you experience an external force changing the direction of your motion.  Seatbelts provide the unbalanced force necessary to stop you when your car stops.