Transcript Standard EPS Shell Presentation

Chapter Six: Laws of Motion
6.1 Newton’s First Law
6.2 Newton’s Second Law
6.3 Newton’s Third Law and
Momentum
6.1 Force changes motion
 A force is a push or pull, or any
action that is able to change motion.
Isaac Newton
Born: England Dec. 25, 1643, the same year Galileo died
Died in 1727, aged 85 years
During Great Plague of 1665, while at home from
college, developed 3 Laws of Motion
Queen Anne knighted him in 1705, to become “Sir”
Newton’s 3 Laws of Motion
6.1 Law of inertia
 Newton’s first law says that objects
continue the motion they already
have unless they are acted on by a
net force.
 If the net force is zero, an object at
rest will stay at rest.
 If an object is acted upon by
unbalanced forces, its motion will
change.
“An object in motion tends to stay in motion;
an object at rest tends to stay at rest.”
Inertia
A moving body will continue moving
in the same direction with the same
speed until some net force acts on it.
A body at rest will remain at rest
unless a net force acts on it.
Summing it up: It takes a net force
to change a body’s velocity.
Demo
What is the
purpose of using a
car seat for a
child?
6.1 Net force
Newton’s first law is
often written in
terms of the net
force:
“An object at rest
will stay at rest and
an object in motion
will continue in
motion at constant
According to these vectors, in
velocity UNLESS
there is a net force.” what direction is the net force?
6.1 Force changes motion
 Forces can be used to increase or
decrease the speed of an object, or
to change the direction an object is
moving.
Inertia Example 2
If you’re driving at 65 mph and have an
accident, your car may come to a stop in
an instant, while your body is still moving
at 65 mph. Without a seatbelt, your inertia
could carry you through the windshield.
Seat belt locking mechanism
6.1 Law of inertia
 Inertia is the
property of an
object that resists
changes in motion.
 Objects with more
mass have more
inertia and are
more resistant to
changes in their
motion.
Which ball has more
inertia?
Inertia and Mass
Inertia of an object is directly related
to its mass
Greater masses have greater inertia,
or a greater resistance to change in
motion
Smaller masses have a lower inertia
Inertia Example 1
An astronaut in
outer space will
continue drifting
in the same
direction at the
same speed
indefinitely, until
acted upon by an
outside force.