Forces Ch. 9.1 Types of Forces

Pearson Online activity

Essential Question: How Do Objects React to Forces? What is force? What are the Main types of Forces? What Factors affect Gravity?

Review…. Acceleration- is the rate at which velocity changes with time. Equation= Final speed- initial speed time Velocity= Speed in a given direction Speed= is the distance an object travels in a given direction Equation= Distance

Vocabulary 9.1 A force: is a push or a pull Applied force: is a force that is put on an object by another object. Normal force: is the force that acts between objects when they are in contact with each other. Friction is the force that two surfaces exert on each other when they rub against each other. Electrical Force is the force between two charged objects. magnetic force the attraction or repulsion between magnetic poles. Gravitational force, or gravity, is a force that pulls objects toward each other. The law of universal gravitation states that the force of gravity acts between all objects in the universe that have mass. Weight is a measure of the force of gravity on an object. Mass is a measure of the amount of matter in an object. Mass

Force Force- a push or a pull. i.e. A force can propel the men into the pool. Applied Force- A force that is put on an object by another object. When she used applied force, she was able to open the container Gravitational force- A force that pulls objects toward each other. Gravitational force pulled the paper toward the floor when it blew off the table. Inertia- Resistance to change in motion. A roller coaster’s inertia makes it hard to stop.

Pg. 329 What is force? 1 objects pulls/pushes another object, then the 1st object exerts (applies) a force on the 2nd. Force is described by its strength and direction. S.I unit for force= NEWTON ( after Sir Isaac Newton)

WHAT IS FORCE? SI unit called the newton (N). A force is a push or a pull. When one object pushes or pulls another object, the first object exerts a force on the second object. EXAMPLE: You exert a force on a chair when you pull it away from a table. Like velocity and acceleration, a force is described by its strength and by the direction in which it acts. Pushing left is a different force from pushing right. The direction and strength of a force can be represented by an arrow. The arrow points in the direction of the force. The length of the arrow tells you the strength of the force. The strength of a force is measured in an SI unit called the newton (N).

Every day you are using forces to act on objects. 2 Main Types of Forces Every day you are using forces to act on objects. The 2 main types of forces are: contact forces forces that act at a distance. Contact forces include: applied forces, the normal force, and friction. force act at a distance include: Electrical force, magnetic force, and gravitational

Types of Force pg. 330 Two main types of forces: Contact forces- (push or force on an object through physical contact.) friction types of surfaces how hard the surfaces are pushed together 2. Forces that act at a distance-

Friction comes from the Greek word- Fricare Friction pg. 331 Brainpop Friction-The force that two surfaces exert (use) on each other when they rub against each other. Factors that affect (change) the force of friction friction types of surfaces how hard the surfaces are pushed together Friction comes from the Greek word- Fricare

Main types of forces To feel the effects of contact forces, an object must touch another object. An applied force is a force that is put on an object by another object. The normal force is the force that acts between objects when they are in contact with each other. Normal here means perpendicular. This force acts perpendicular to the surface of contact such as the wall that pushes back and supports you when you lean against it.

Did You Know? The Daytona 500 is tires on the race cars can heat up to 93one of the biggest racing events in the world. Cars race along the track at over 322 km/h (200 mph). This kind of speed generates so much friction that the degrees Celsius (200 degrees Farenheit).

Forces acting at a distance pg. 332 Some forces push or pull an object without touching the object. Types of forces at a distance: Electrical force- forces between charged objects positive(+) charge= proton negative (-) charge= electron If a proton= + which carries a positive charge , is near an electron, which carries a negative charge, they attract one another. Magnetic Force- The attraction or repulsion between magnets poles. Gravitational Force- A force that pulls objects toward each other (force that pulls objects straight down toward the center of the Earth)

Magnetic Poles Positive + Negative -

Magnetic force

Law of Gravitation For example: The law of universal gravitation states that the force of gravity acts between all objects in the universe that have mass. So, any two objects in the universe that have mass attract each other. For example: you and your pencil are attracted to each other. However, you do not notice the attraction between such small objects as you and your pencil because these forces are extremely small compared to the force of Earth’s attraction. You observe only the effects of the strongest gravitational forces.

Factors that Affect Gravity pg. 333 Gravity acts everywhere in the universe (not just on Earth) i.e. Skydivers fall to the ground Moon orbiting around Earth Keeps all planets orbiting around the sun Law of Universal Gravitation--- The scientific law that states that every object in the universe attracts every other object. Any 2 objects that have mass (how much matter is in an object) attract each other.

Factors Affecting Gravity pg. 334 Brainpop- Gravity G.F. is present in any 2 objects in the universe Two factors that affect gravitational attraction are _______________ and _______________. The more mass an object has, the greater its gravitational force. The shorter the distance is between two objects, the stronger the gravitational force between the objects. Bigger mass= greater gravitational force between objects. As distance increases between objects= (-) less gravitational force S.I. Unit Mass = Kilogram

Weight and Mass pg. 335 Weight is a measure of the force of gravity on an object. Mass is a measure of the amount of matter in an object. Mass is the same on Earth as it would be on any other planet. But weight would vary on each planet, since each planet’s gravitational force is different. At any given time, mass stays the same (amount of matter in an object) BUT weight varies with the strength of _________ ___________________.

Types of Forces Gravitational Attraction Gravitational attraction depends on two factors: mass and distance. Compare the gravitational force between different planets and their sun.

Types of Forces Weight and Mass The Mars Phoenix Lander weighs about 3,400 N on Earth. It weighs about 1,300 N on Mars. If the dog weighs 60 N on Earth, what would he weigh on Mars and the moon?