90 likes | 181 Vues
BELLRINGER. 5b. How should the thermometer be placed in the beaker to get a more accurate measurement of the solution’s temperature?. 5a. How will the temperature reading on the thermometer be affected by following the technique shown in the diagram?.
E N D
BELLRINGER 5b. How should the thermometer be placed in the beaker to get a more accurate measurement of the solution’s temperature? 5a. How will the temperature reading on the thermometer be affected by following the technique shown in the diagram? Answer BOTH A & B! You do NOT have to use full sentences but DO spell correctly!
House Keeping • Supply Check • Take attendance • Excel info • Hand out tickets if applicable • Thank you to… • Recycling • HW: READ CHAPTER 4, PAGES 94-115 in the book • The Curse of Knowledge
Forces August 25, 2010
Basic definitions & symbols • ∑ = “the sum of” • Vector= a straight line representing the direction of a push or pull (can be added) • Newton = the unit of force • N = kg * m s2 • “Normal” = perpendicular
Force Concepts • Forces are represented by arrows drawn from the center of mass of the object being analyzed • The length of a vector is proportional to the amount of force used • Ex. 1cm = 10 Newtons; 3.5cm = 35 Newtons • NO other vectors are ever drawn from the center of an object (ex. velocity or acceleration) because these other vectors are the RESULT of a force • Every force will have 2 subscripts • The first is the object on which a force is applied • The second represents the object applying the force
Main Forces • WOE = “weight” = — mg • force on an object by the gravity of the earth • NOS = “normal force” = +mg • the contact force that keeps objects from moving through one another • ALWAYS at a right angle to the surface of an object • Force on the object by the surface • fOS= “frictional force”= µN • ALWAYS parallel to the surface • Force on the object by the surface
Main Forces (cont’d) • TOR= “tension force” • A tension ALWAYS pulls; can not be applied to springs • Force on an object by a rope • FOA= “applied force” = ma • An external force applied to an object • This is normally given without saying where it’s coming from • The force on an object by an applied source • ***Whenever there is an acceleration, there HAS to be a force***
Free Body Diagram • A free body diagram is the visual representation of force vectors Fnet = manet NOS = + mg fOS = µN FOA = ma WOE = — mg ∑ Fy = mg - mg = 0 ∑ Fx = ma - µN = manet
Castro’s Guide to Forces • #1 & 2 together • 10 minutes to complete • #3 & 6 Groups 1, 4, 7 • #4 & 7 Groups 2, 5, 8 • #5 & 8 Groups 3, 6, 9