2 First we need to define the word FORCE: The cause of motion (what causes objects to move)Two types of forces- Pushes- Pulls
3 Forces are measured in Newtons SI unit of forceSymbol: NMeasured by using a spring scale
4 Forces may be balanced or unbalanced Balanced forces – all forces acting on an object are equal-There is NO MOTIONUnbalanced forces – one or more forces acting on an object are stronger than others-There is MOTIONA NET FORCE
5 Friction Force that slows down motion. There are three different types of friction:1. Rolling Friction2. Sliding Friction3. Fluid Friction
6 Rolling FrictionThe friction that exists when a wheel turns on a surface.
7 Sliding FrictionWhen two objects are rubbing against each other.
8 Fluid FrictionThe friction on a solid object as it moves through water.
9 Gravity Force that attracts all objects toward each other More mass = more gravityAcceleration because of gravity is 9.8 m/s/sAll objects accelerate at the same rate
10 Newton’s Laws First Law – Inertia Second Law – Acceleration, Force & MassThird Law – Action-Reaction
11 First LawInertiaAn object at rest [not moving] remains at rest unless acted on by a force [push or pull]An object in motion remains in motion unless acted on by a force [push or pull]
12 First Law Inertia & Mass Mass is the amount of matter in an object The more MASS an object has, the more INERTIA the object has.Bigger objects are harder to start & stop
13 Second Law Acceleration & Force Acceleration & Mass The more force placed on an object, the more it will accelerate [change its motion]Acceleration & MassThe more mass [or inertia] an object has, the more force it takes to accelerate the object
14 Third Law Action – Reaction Forces are always produced in pairs with opposite directions & equal strengthsFor every force there is an equal and opposite force