2 CHAPTER 4 ESSENTIAL QUESTIONS What are Newton’s Laws of Motion?How do forces cause motion?How can the Law of Universal Gravitation be applied?How can one weigh the earth?What effect does friction have on the motion of an object?
4 Force Facts Basic definition: a push or a pull Can we do a better job? Probably.An interaction between bodies.Forces can be classified by two types;1. Contact Forcei.e. Normal, Tension, Friction2. Field Force (at-a-distance)i.e. Gravitational, Magnetic, electric
5 Newton’s First Law The Law of Inertia The natural tendency for all objects is motionNewton’s First Law (N.F.L.)An object remains at rest or in a state of motion at constant speedalong a straight line unless compelled to change that state by a netforce (SF).Forces are balancedObject at restvo = 0 m/sObject in motionv m/s/sa = 0 m/s/sa = 0 m/s/sObject in motionSame speed/directionStays at rest
6 Inertia Inertia – Tendency to resist motion The more massive an object is, the more inertia it will haveIt is harder to get boulder in moving (also harder to stopthe boulder from moving) than it is to bet a pebble movingInertia is a quantity that is dependent upon the mass of the object
7 Free Body Diagrams (FBD) A pictorial representation of all of the forces acting on an objectNNormal force (N): Surfaceforce that is always drawnperpendicular to thesurfaceTfWeight (mg): Always drawnStraight down from centermgTTension (T): Force inropes/chains drawnaway from objectFriction (f): Drawnopposing motionmg