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Forces
What is a force?
 Force
a push or pull on an object
 Forces
are described by how strong
they are and the direction in which
they act.
Unbalanced Forces
 Unbalanced
forces acting on an object
will cause an object to start moving,
stop or change directions.
Inertia
 Inertia
is the tendency of an object to
resist change in its motion.
Newton's First
Law
 An
object at rest tends to stay at rest
and an object in motion tends to stay
in motion unless acted upon by an
unbalanced force.
Mass
 Mass
is the amount of matter in an
object. Not it's weight.
 Mass is measured in Kilograms
 The greater an objects mass the greater
it’s inertia.
Newton’s Second Law
 The
net force on an object is
equal to the product of it’s
acceleration and it’s mass.
 force
= mass x acceleration
Friction
 The
force that one surface exerts on
another when the two surfaces rub
against each other.
 The strength of friction depends on The types of surfaces involved
 How hard the surfaces push
together.
Three Kinds Of Friction
 Sliding
frictionsolid surfaces
sliding over each
other.
Three Kinds Of Friction Cont.

Rolling friction-a
round solid object
rolling over a
surface.
Three Kinds Of Friction Cont.
 Fluid
friction- a
solid object
moving through
a liquid or a gas
Gravity
 The
force that pulls objects toward
each other.
 Free
fall- when the only force acting
on an object is gravity.
Gravity Continued
 Acceleration
of objects in free fall is
9.8 m/s².
 Objects falling through air experience
a fluid friction called air resistance.
Weight
What is the difference between mass and
weight?
 Mass is the amount of matter in an object.
 Weight is a measure of the force of gravity on
an object.
 Weight =mass X acceleration due to gravity.
 In science weight is measured in Newtons.
