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Download Lesson 1 - Gravity and Friction
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A push or pull on an object. Described by: •STRENGTH •DIRECTION A force gives an object energy to: •STOP MOVING •START MOVING •CHANGE DIRECTION Contact Force Non Contact Force Contact How do these relate to the title of this lesson? (Gravity and Friction?) Noncontact Contact = friction Noncontact = gravity A push or pull on one object by another that is touching it. Contact forces can be: Strong OR Weak A force that one object can apply to another object without touching it. Examples Include: Gravity Magnetic Force Electric Force ARROWS can be used to show forces. LENGTH The of an arrow shows the STRENGTH of the force. The DIRECTION that the arrow points shows the direction in which the FORCE WAS APPLIED The stronger the force the LONGER the arrow. The SI unit for force is the NEWTON The symbol for Newton is N One Newton = about the force you exert to lift a lime. Named after: Sir Isaac Newton (founder of physics) An attractive force that exists between all objects that have mass. On EARTH the force of gravity = 9.8 m/s2 All objects fall to the Earth at an acceleration of 9.8m/s2 due to the force of gravity. 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 •DISTANCE The amount of matter in an object. When the mass of one or both objects INCREASES the gravitational force between them also INCREASES Regardless of the amount of mass an object has the FORCE ARROWS will be the SAME SIZE Each object exerts the other object. SAME attraction on the The attraction between objects DECREASES as the DISTANCE between the object INCREASES The gravitational force exerted on an object. Weight is measured in NEWTONS Near Earth’s surface the object’s weight is the FORCE DUE TO GRAVITY Weight and mass are related, but ARE NOT the same. Weight can CHANGE due to GRAVITY Mass DOES NOT change FORCE = MASS x ACCELERATION F= MxA Weight on Earth = MASS x 9.8m/s2 (acceleration due to the force of gravity) What would an object with a mass of 10 kg weigh? If your mass was 50kg, what would your weight be? 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. 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 ADDED Forces moving in the opposite direction are SUBTRACTED Forces acting on an object that combine and form a net force of ZERO. NO change in motion. A force that resists the motion of two surfaces that are touching. Types of friction •STATIC FRICTION •SLIDING FRICTION •FLUID FRICTION Friction that acts on objects that are not moving. When solid objects slide over each other. A force produced by a fluid (gases or liquids) Examples: engine oil, grease Air resistance •a type of fluid friction •Upward force exerted on falling objects. Air resistance is affected by: •SHAPE •SIZE •MASS *objects with more surface area have more air resistance** 2 causes of friction When microscopic dips and bumps that cover surfaces slide past another surface with dips and bumps they catch on to one another. When a positive charge slides by a negative charge attraction occurs.
