Newton's Laws

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