Download Mass vs. Weight and Newton`s Second Law

INERTIA is the tendency of an object to
resist changes in their state of motion.
Mass is a measure of inertia.
Object with small mass -----> has less inertia
Object with large mass --------> has more inertia
Ex: Imagine how difficult playing softball with a bowling
ball.
1.
2.
Hard to pitch
Hard to change its direction
Mass is the measure of the inertia of
an object
 The more mass an object has, the harder
it is to move it (or stop it)
Mass ≠ Weight
Weight changes due to gravity
 You can be “weight-less” in space...but
you’re not mass-less!
MASS is a measure of the amount of
matter in an object
• Mass will not change as you move from place to place
WEIGHT is a measure of the gravitational
force exerted on an object
(the force with which Earth’s gravity pulls on a quantity of
matter)
• The force varies from place to place
• Ex: Weight of an object will be different on Earth than on the moon
Mass is a PROPERTY
 Measured in kilograms (kg)
Weight is a FORCE
 Measured in newtons (N)
A force, in simple terms,
is either a push or a pull
 Would pushing a car be any easier
on the moon?
 No!
 The car has the same mass, even if
the weight is lighter
•An action exerted on an object (a push or a pull)
in order to change the state of rest or motion
of an object.
•Measured in Newtons (N)
Net Force:
• Combination of all the forces acting on
an object. (add them up)
 If all of the pushes and pulls are even on an object, then the
object “keeps on doing what it was doing”
• Tug-o-war
 Two teams that are evenly matched
play tug-o-war
 NOTHING HAPPENS
Balanced Forces
when net force is zero
Does not cause a change
in object’s motion
Unbalanced forces cause
objects to change velocities
Tug-o-war
 Two teams that are unevenly matched
play tug-o-war
 One team will win
What happens when an object has an unbalanced
force acted upon it?
Unbalance forces cause acceleration!!
Equal –
Nothing happens
Ex: A book sitting on a shelf
 Fg = 25 N
 FN = 25 N
Unequal –
The object changes what it is doing
Ex:
 FA = 25 N right
 FA = 100 N left
The acceleration of an object is directly proportional
to the net force acting on the object and is
inversely proportional to the mass of the object.
In other words:
F=
mass x acceleration
F=ma
Fg
m
“Weight”
g
m
g