2 Forces… Forces are vectors Net Force Have both magnitude and directionsNet ForceVector sum of all forces acting on a bodyWhen the net force on an object is zero, the object is in equilibriumIn otherwords, the acceleration is zero.
3 Force & Motion Forces cause accelerations Change in velocity Speed and/or directionConsider the book on the table. In order for the book to move, an unbalanced force has to act on the book.
4 SystemsWhen considering how a force affects motion, it is important to identify the object of interest. This object is called the system.Everything around the object that exerts forces on it is called the external world.The identifiable cause is called an agent.
5 Contact ForcesA contact force exists when an object from the external world touches a system and thereby exerts a force on it.TensionFrictionAppliedNormal
6 Field Forces Field forces are exerted without contact. Electrical Also known as non contact forces or action at distances forcesMagneticGravitationalElectrical
12 Inertia An object’s resistance to change its state of motion. An object’s mass is a measurement of the object’s inertia.The more mass an object has, the more resistance it will have to change its state of motion.
13 Mass vs. Weight Mass Weight Amount of matter present in an object Constant – same everywhere in the universeA measurement of an object’s inertiaMeasured using a BALANCEWeightForce due to gravityW = mgChanges as the acceleration due to gravity changesMeasured using a SCALE
14 Newton’s 2nd LawAcceleration is directly proportional to the net force acting on the object and inversely proportional to the object’s mass.F = ma
15 F = ma F = force m = mass a = acceleration Measured in Newtons Measured in kilogramsa = accelerationMeasured in m/s2
16 Newton’s 3rd LawFor every action force there is an equal and opposite reaction force.
17 Interactions All forces result from interactions between objects. Action-Reaction force pairs act on different objects.Action-Reaction forces do NOT cancel out because they act on different objects.