Force & Motion 3Force & Motion 3

Weight and MassWeight and Mass

Mass is the Mass is the measure of the measure of the inertia of an object inertia of an object and depends on and depends on the amount of the amount of matter the objects matter the objects containscontains

Weight and MassWeight and Mass

Weight is the force of gravity acting on an Weight is the force of gravity acting on an objectobject

Weight and MassWeight and Mass

An objects weight An objects weight is the product of is the product of the mass and the mass and acceleration due to acceleration due to gravity acting on itgravity acting on it

W = m W = m g g F = m F = m a a g = 9.8 m/s²g = 9.8 m/s²

Newton’s 3Newton’s 3rdrd Law Law

Whenever one object exerts a force on a Whenever one object exerts a force on a second object, the second object exerts an second object, the second object exerts an equal and opposite force on the first objectequal and opposite force on the first object

Newton’s 3Newton’s 3rdrd Law Law

Force exists in Force exists in pairspairs

Action and Action and ReactionReaction

Newton’s 3Newton’s 3rdrd Law Law

THINKTHINK

If a marble were If a marble were moving 100 times moving 100 times faster then a faster then a shopping cart, shopping cart, which would be which would be easier to stop?easier to stop?

Newton’s 3Newton’s 3rdrd Law Law

The action and The action and reaction forces do reaction forces do not always act on not always act on the same objectthe same object

Newton’s 3Newton’s 3rdrd Law Law

Momentum = the object’s mass Momentum = the object’s mass objects velocity objects velocity

M = m M = m v v

Measured in kg-m/secMeasured in kg-m/sec

Newton’s 3Newton’s 3rdrd Law Law

Conservation of momentumConservation of momentum If no net force acts on a system, then the If no net force acts on a system, then the

total momentum of the system does not total momentum of the system does not changechange

Newton’s 3Newton’s 3rdrd Law Law

Conservation of Conservation of momentummomentum

In a closed system, In a closed system, the loss of the loss of

momentum of one momentum of one object equals the object equals the

gain in momentum gain in momentum of another objectof another object