The Laws of Motion Essential Question: How do forces change to motion of an object? Original ppt from Mrs. West’s 8th Grade Physics Website http://kawameeh.twpunionschools.org/subsites/hbormann/index.html Adapted by Denise Poston 2015

True or False. What do you think True or False? What do you think? Only some of the statements below are true. Can you identify them?

Force A push or pull on an object. Described by: A force gives an object energy to:

Types of Force Contact Force Non-Contact Force

Types of Force Contact Force Noncontact Force Contact forces can be: A force that one object can apply to another object without touching it. A push or pull on one object by another that is touching it. Contact forces can be: Examples Include:

Strength and Direction of Forces can be used to show forces. The of an arrow shows the of the force. The that the arrow points shows the direction in which the The stronger the force the the arrow.

Strength and Direction of Forces The SI unit for force is the The symbol for Newton is One Newton = about the force you exert to lift a lime. Named after:

Friction A force that resists the motion of two surfaces that are touching. Types of friction

Static Friction Friction that acts on objects that are not moving.

Sliding Friction When solid objects slide over each other.

Fluid Friction A force produced by a fluid (gases or liquids) Examples: engine oil, grease Air resistance Air resistance is affected by: *objects with more surface area have more air resistance* a type of fluid friction

What causes friction? 2 causes of friction Surface roughness (texture) Attraction between particles (positive and negative)

Gravity Force of gravity An attractive force that exists between all objects that have mass. Force of gravity On EARTH the force of gravity =____________ All objects fall to the Earth at an acceleration of 9.8 m/s2 due to the force of gravity.

The Law of Universal Gravitation Sir Isaac Newton (1600’s) The law states: Factors Affecting Gravity All objects are attracted to each other by a gravitational force. The strength of force depends on the MASS of each object and the DISTANCE between them.

Mass Which object has more mass? Which object has more mass? The amount of matter in an object. Which object has more mass? Which object has more mass?

Gravitational Force and MASS When the mass of one or both objects the gravitational force between them also Regardless of the amount of mass an object has the will be the Each object exerts the attraction on the other object.

Gravitational force and DISTANCE The attraction between objects as the between the object

Weight The gravitational force exerted on an object. Weight is measured in Near Earth’s surface the object’s weight is the

Weight and Mass on Earth Weight and mass are related, but ARE NOT the same. Weight can due to Mass change FORCE = F = Weight on Earth =

Examples: What would an object with a mass of 10 kg weigh on Earth? If your mass was 50kg, what would your weight be on Earth?

Net Force The combination of all the forces acting on an object. To calculate the net force: If the forces act in the same direction they are added together. If forces act in opposite directions they are subtracted.

Combining Forces - _____________ Forces acting on an object that combine and form a net force that is not zero. Unbalanced forces cause an object to move. Forces moving in the same direction are Forces moving in the opposite direction are __________ ______________

Combining Forces – __________________________________ Forces acting on an object that combine and form a net force of ZERO. NO change in motion.

Any last revisions? Rewrite any false statements to make them true.