Forces

First we need to define the word FORCE: The cause of motion (what causes objects to move) Two types of forces - Pushes - Pulls

Forces are measured in Newtons SI unit of force Symbol: N Measured by using a spring scale

Forces may be balanced or unbalanced Balanced forces – all forces acting on an object are equal -There is NO MOTION Unbalanced forces – one or more forces acting on an object are stronger than others -There is MOTION A NET FORCE

Friction Force that slows down motion. There are three different types of friction: 1. Rolling Friction 2. Sliding Friction 3. Fluid Friction

Rolling Friction The friction that exists when a wheel turns on a surface.

Sliding Friction When two objects are rubbing against each other.

Fluid Friction The friction on a solid object as it moves through water.

Gravity Force that attracts all objects toward each other More mass = more gravity Acceleration because of gravity is 9.8 m/s/s All objects accelerate at the same rate

Newton’s Laws First Law – Inertia Second Law – Acceleration, Force & Mass Third Law – Action-Reaction

First Law Inertia An 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]

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

Second Law Acceleration & Force Acceleration & Mass The more force placed on an object, the more it will accelerate [change its motion] Acceleration & Mass The more mass [or inertia] an object has, the more force it takes to accelerate the object

Third Law Action – Reaction Forces are always produced in pairs with opposite directions & equal strengths For every force there is an equal and opposite force