Newton's Laws describe the motion of and forces on objects. Newton's First Law states that objects in motion tend to stay in motion and objects at rest tend to stay at rest unless acted upon by an unbalanced force. Newton's Second Law states that the acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the object's mass. Newton's Third Law states that for every action, there is an equal and opposite reaction.

1. Newton’s Laws
An Instructional Slideshow
by George Souflis

2. Newton’s First The puck, as with all objects,
Law tends to move at a constant speed
and in a straight line. After you hit
In this picture the hockey puck the puck it is moving entirely by
demonstrates Newton’s first law as it this tendency that we call inertia.
moves across the smooth, !ictionless
table. The puck would move infinitely
on its straight path at this speed,
but it hits the table’s edge.

3. So to review...
• Objects (like the hockey puck) tend to do what
they’re already doing, and this is called inertia.
• If something is moving North at 5 miles per
hour, it’s going to continue going North at 5
miles per hour...
• ...UNLESS

4. In these next pictures we see a The skateboarder is moving at a
skateboarder riding along a smooth, flat constant speed in a straight line by
road. When the skateboarder hits the his own inertia. In other words,
rock, it demonstrates the second part there is no force continuing the
of the First Law. skateboard’s motion. The rock
hitting the skateboard, therefore,
exerts a force that is unbalanced.
This stops the skateboard’s path
down the road.
The rock hitting the skateboard exerts a force
that is unbalanced - since there is no force
moving the skateboard. The skateboarder,
however, has not had a force to stop it, and will
continue forward at the skateboard’s original
velocity.

5. To Sum It All Up...
• Newton’s First Law deals with an object’s
tendency to keep doing what it’s already doing
(inertia)
• An object can change what it’s doing when an
unbalanced force acts on it.

6. Newton’s
Second Law
In this next picture we
can see the Second Law
at work. If the two rocks
are pulled with equal
force, the rock with less
mass will have more
acceleration. For the
rocks to accelerate
equally, the more massive
rock must have a larger
force acted on it.

7. Here we see another
example of the Second Law.
To be accelerated (as when
being tackled), a massive
football player needs a large
force acting on it. In same
way, a less massive football
player with high
acceleration also exerts a
large force.

8. To Sum It All Up...
• To generate the same acceleration, more
massive objects require more force.
• The same force can be generated by a less
massive object with more acceleration and a
more massive object with less acceleration.

9. Newton’s Third
Law
In this picture we can see
Newton’s Third Law. The
diver pushes down on the
diving board. At the same
time the diving board pushes
up on the diver. In this way,
all forces work in pairs.

10. In this picture we can see
another example of the Third
Law. As the man uses the
paddle to push water
backwards, the canoe moves
forward. This is because of the
pair of forces that act on the
paddle. In this way it is clear to
see that the pairs of forces are
both opposite in direction and
equal in magnitude.

11. To Sum It All Up...
• All forces come in pairs that are equal and
opposite.

12. Those are Newton’s Three
Laws!
The End.