Galileo showed that all objects accelerate at the same rate when falling, due to gravity, regardless of their mass. Heavier objects experience a greater force of gravity but require more force to accelerate them, so the acceleration is the same. Acceleration is the rate of change of an object's velocity over time and is directly proportional to the net force acting on an object and inversely proportional to its mass, as stated in Newton's Second Law of Motion. Newton's Three Laws of Motion describe the relationship between an object's motion and the forces acting upon it.

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 balances additional force of
gravity so all objects will fall at same rate
• Acceleration – rate at which velocity
change over time (either speed or
direction)

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)
• Vacuum – place where there is no matter
(space)
• Orbit – forward motion with a change in
velocity (direction)

6. • 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

7. • Mass is a measure of inertia – the greater
the mass the greater force of inertia
• 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

8. • 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
• 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

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

10. • 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.

11. • 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 3 law)

12. Identify the Law