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Chapter 10 Forces
Force and Net Force
• Force is a push or a pull on
an object.
• Net force is the total force
on an object.
Unbalanced Force
Balanced Force
• Unbalanced Force
can cause an
object to move,
stop moving, or
change direction.
• The balanced
forces are the
forces in equal
and opposite
directions.
Forces change
motion.
• HMM….
Can you
see the
unbalanced
force here?
•
Newton’s First Law
Inertia
–An object at rest
Greater mass
will stay at rest
means
unless acted upon by
an outside force.
Greater inertia
–Inertia is every
objects resistance
to change its
motion.
•Take out a
piece of paper
and label it
“Inertia Mini
Lab”
Newton’s Second
Law
• The acceleration of an object is
directly proportional to the net force
acting on the object and inversely
proportional to the object’s mass.
Force=mass x acceleration
F=m x a
• Or
• a = Force/ mass
• a = F/m
Equation for Newton
It’s the same
as the force
equation!
•Newton=m x a.
Force and mass
determine
acceleration.
Luke! Use the
mass times
the
acceleration!
Sometimes we might calculate
mass using Force and
Acceleration
• Mass=Force/Acceleration
• m=F/a
How much Force was required to
make a 2000kg car accelerate at
5m/s/s?
1. 400N
2. 0.001N
3. 10,000N
•Force=Mass x acceleration
•F=ma
•F=2000kg x 5m/s/s
•a= 10,000N or kgxm/s/s
33%
1
33%
2
33%
3
•
If you drop a 15kg bowling ball
with a Force of 147N, what is it’s
33% 33%
acceleration?
3
0
1. 9.8m/s/s
2. 0.1m/s/s
3. 2,205m/s/s
•
0
33%
•Acceleration=Force/Mass
•a=F/m
•a=147kgxm/s/s÷15kg
•a= 9.8m/s/s
1
2
3
A person throws a baseball at an
acceleration of 25m/s/s with
12.5N of Force. What’s the Mass
of the ball?
33% 33%
1. 312kg
2. .5kg
3. 2kg
33%
•Mass=Force/Acceleration
•m=F/a
•a=12.5kgxm/s/s÷25m/s/s
•a= .5kg
1
2
3
4 Types of Friction
• The 4 types of friction are:
1. Sliding friction (strongest)
2. Rolling friction
3. Fluid friction (weakest).
4. Static friction
• What
type of
friction?
•What
type of
friction?
•What
type of
friction?
What type of friction?
2 Factors of Friction
• 1-Type of surface.
• 2-How hard the two
surfaces push together.
•
Which type of hockey has
more friction?
Air Resistance
and Weight
• Air resistance is a type
of fluid friction on falling
objects. Weight is the
force of gravity on an
object at the surface of
the Earth.
Law of Universal
Gravitation
• Gravity acts between all
objects in the universe.
Gravity Between Objects
• The force of gravity between objects
increases with greater mass and decreases
with greater distance.
•
• Gravity is the
force that pulls
objects toward the
Earthacceleration due
to gravity is
9.8m/s/s.
Newton’s Third law
• If an object exerts a force
on another object, the
second object, exerts an
equal force in the
opposite direction.
Momentum
• The momentum of an object
is the product of its mass and
velocity.
• In other words:
Momentum = mass x velocity
• Kg x m/s
COLLISIONS
Law of Conservation of
Momentum
• The total momentum of
the objects that interact
does not change.