1. Newton’s First Law of
Motion
Inertia- the tendency of an object
to resist change. The greater the
mass the greater the inertia!
2. Force
• Force- Push or a pull on
an object
– Object speeds up, slows
down, or turns from force
• More than one force can act
on an object at the same time
• Net Force- Combination
of all the forces acting on
an object.
• Force= Mass X Acceleration
3. Balanced and Unbalanced Forces
• Balanced Forces- Two or
more forces exerted on
an object that cancel
each other and do not
change object’s velocity
– Net force is zero
• Unbalanced Forces-
Effects of the forces don’t
cancel and the object’s
velocity changes
– Net force is not zero
4. Newton’s First Law of Motion
• Isaac Newton (1642-1727)-
Explained motion of objects in
3 laws of motion
• Newton’s First Law of Motion-
An object at rest will stay at rest,
an object in motion at constant
velocity will continue at a
constant velocity unless acted
upon by an unbalanced force.
5. Friction
• Friction- Force that
acts to resist sliding
between two touching
surfaces.
– Ex: Acts on objects
moving through air or
water
6. Friction
• Static Friction- Type of friction that prevents an
object from moving when force is applied.
(object at rest)
– Caused by attraction of atoms on the two surfaces
that are in contact
7. Friction
• Sliding Friction- Type of friction that is due to the
roughness of the two objects.
– Slows down object that slides
