force mass

1. Gravity and Motion
 Aristotle (400BCE) – rate
of acceleration
depended on mass
 Galileo (late 1500’s) –
mass of an object does
not affect the rate at
which an object falls
 Why? Acceleration
depends on force and
mass

2. Heavier object experiences greater force
of gravity, however, it takes more force
to accelerate
Heavier mass is balance by additional
force of gravity so all objects will fall at
same rate
Acceleration – rate at which velocity
(either speed or direction)change over
time
Video

3. All objects accelerate
toward earth at
9.8m/s2
. which
means…
For every second
object falls, downward
velocity increases by
9.8 m/s
Air resistance – force
that opposes motion
through air

4. Air resistance depends on size,
shape and speed
Speed of a falling object increases,
air resistance increases
The upward force of air resistance
continues to increase until it is equal
to the downward force of gravity and
the net force = 0, the object stops
accelerating

5. Terminal velocity – constant velocity
of a falling object
Free fall – happens only when gravity
is acting on an object (no air
resistance) occurs in space or a
vaccuum
Vacuum – place where there is no
matter (space)
Orbit – forward motion with a change
in velocity (direction)

6. Example:
parachute
increases air
resistance of a
sky diver and
slows him to safe
terminal velocity

7. Centripetal force – force that causes
objects to move in a circular path
Projectile motion – curved path that an
object follows when thrown, launched or
otherwise projected near the earths
surface – consists of horizontal and
vertical motion
Inertia – the tendency of all objects to
resist any change in motion

8. Newton’s 3 Laws of Motion
 Newton’s First Law of
Motion – Law of inertia
 An object at rest remains at
rest, and an object in motion
remains in motion at a constant
speed and in a straight line
unless acted on by an
unbalanced force
 Mass is a measure of inertia –
the greater the mass the greater
force of inertia

10.  Newton’s Second Law of Motion –
The acceleration of an object
depends on the mass of the
object and the amount of force
applied.
Formula: F= m x a
 Acceleration depends on mass – as
mass increases, the amount of force
need to accelerate an object
increases
 Acceleration of an object is always
in direction of the force applied

11. Units for Calculation
 Force = N (newton)
 Mass = Kg
 Acceleration = m/s2

13. Newton’s Third Law of
Motion
Whenever one object exerts a
force on a second object the
second object exerts an equal
and opposite force on the first
object
Sometimes called the
“action / reaction” law
States that all forces work in
pairs.

15.  Momentum – product of the mass
and velocity of an object ( p = m x
v )
 The Law of Conservation of
Momentum
 Momentum can not be gain or lost,
only transferred
 Any time objects collide, the total
amount of momentum stays the same.
(Newton’s 3rd law)

16. Identify the Law