Sir Isaac Newton (1642 – 1727)
Newton was an English
physicist, considered one of
the most important scientists
of all time. Newton formulated
laws of universal gravitation
and motion—laws that explain
how objects move on Earth as
well as through the heavens.
He established the modern
study of optics—or the
behavior of light—and built
the first reflecting telescope.
• A force is a push or a pull.
• In honor of Newton’s work with
motion, the unit of force in the
metric system is named for him.
• One newton is the amount of force it
takes to accelerate a one kilogram
mass at a rate of 1 meter/second 2.
• 1 n = 1kg-m/s2
Newton’s First Law (Part 1)
(Law of Inertia)
An object at rest remains
at rest unless acted on
by an outside
Weight and Mass
• Weight is the • Mass is the amount
force with which of matter
gravity pulls an contained in an
object downward. object.
• Units: • Units:
– Metric – Newton (n) – Metric – kilogram
– English – pound (lb) (kg)
– English - slug
• Varies depending
on the object’s • Remains constant
Newton’s First Law (Part 2)
• An object in motion remains in motion
unless acted on by an outside
• What does it take to keep an object
in motion (ignoring friction)?
Both the car and its driver are traveling at 30 mph.
When the car stops suddenly, the driver continues
at 30 mph. Why?
Newton’s Second Law
• If there is an unbalanced force,
there will be an acceleration.
• The size of the acceleration depends
– the mass of the object
– the size of the force
• This is usually written F = ma or
a = F/m
Larger Forces Cause Larger
Mass: 1545 kg
Horsepower: 395 hp
0 – 60 mph: 4.5 s
Mass: 1545 kg
Horsepower: 192 hp
0 – 60 mph: 8.4 s
Larger Masses Cause Smaller
Baseball mass = 0.14 kg (.32 lbs)
Distance = over 90 m (300 ft)
Shot put mass = 7.26 kg (16 lbs)
Distance = 23.12 m (75 ft)
Newton’s Third Law
(Law of Action – Reaction)
• For every action there is an equal and
• If object A exerts a force on object
B then object B exerts an equal force
in the opposite direction on object A.