Newton's first Law

1. Newton’s
1st Law of Motion
8th Grade Science

2. Newton’s 1st Law of Motion
This law is AKA "the law of inertia".
An object at rest will remain at rest
unless acted on by an unbalanced force.
An object in motion continues in motion
with the same speed and in the same
direction unless acted upon by an
unbalanced force.

3. Newton’s 1st Law of Motion

4. What Does it Mean?
This means that there is a
natural tendency of
objects to keep on doing
what they're doing. All
objects resist changes in
their state of motion. In
the absence of an
unbalanced force, an
object in motion will
maintain this state of
motion.
These pumpkins will not move unless
acted on by an unbalanced force.

5. Example
 Once airborne, unless
acted on by an
unbalanced force (gravity
and air – fluid friction), it
would never stop!
 Unless acted upon by an
unbalanced force, this
golf ball would sit on the
tee forever.

6. WAIT!
Then why do objects in
motion slow down and then
stop without an outside force?

7. Critical Writing (Think, Pair, Share)
Remember the forces we talked about
last week?
Write down possible forces acting on
the object that we can’t see.

8. Friction in Action
Slide a book across a
table and watch it slide to
a rest position. The book
comes to a rest because of
the presence of a force -
that force being the force
of friction - which brings
the book to a rest
position.

9. Why Does it Stop?
In the absence of a force of
friction, the book would
continue in motion with the
same speed and direction -
forever! (Or at least to the end
of the table top.)

10. 1st Law in Action
You have 1 minute to discuss the questions with your shoulder partner:
1. What is the motion in this picture?
2. What is the unbalanced force in this picture?
3. What happened to the skater in this picture?

11. Newton’s 1st Law in Action
Don’t let this be you. Wear seat belts!
Because of inertia, objects (including you) resist changes
in their motion. When the car going 80 km/hour is
stopped by the brick wall, your body keeps moving at
80 km/hour.

12. Penny and Cup
Demonstration
Product: How does this demo
relate to Newton’s 1st Law of
motion? (complete sentences)