2 KEY CONCEPTS AND QUESTIONS- objectives What are some contact forces and some noncontact forces?What is the law of universal gravitation?How does friction affect the motion of two objects?What are the different types of friction?
3 VOCABULARY force friction contact force noncontact force gravity mass weight
4 GRAVITY AND FRICTION Force- a push or pull applied to an object. (N) Contact - a force on one object by another object that is touching it.Noncontact – a force applied to an object without touching it- gravity, electric force, magnet to metal
5 GRAVITYAttractive force that exists between all objects that have mass.Law of Universal Gravitation – The strength of the gravitational force depends on the mass and distance of each object.WEIGHT- The gravitational force exerted on an object (measured in Newtons)
6 FRICTION TYPE OF FRICTION DESCRIPTION EXAMPLE STATIC TWO SURFACES ARE NOT MOVING PAST EACH OTHERPUSHING HEAVY OBJECTSLIDINGTWO SURFACES SLIDE PAST EACH OTHERSLEDDING DOWN A HILLROLLINGROLLING OBJECT AND SURFACE IT ROLLS UPONSKATEBOARD MOVING ON GROUNDFLUIDOBJECT MOVES THROUGH A FLUID- GAS OR LIQUIDSKYDIVINGFRICTIONIT IS A FORCE THAT RESISTS THE MOTION OF TWO SURFACES THAT ARE TOUCHING
7 AIR RESISTANCEIS A FRICTION-LIKE FORCE THAT OPPOSES MOTION OF OBJECTS THAT MOVE THROUGH AIR. DEPENDS ON SPEED, SIZE, AND SHAPE OF OBJECT.