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 ForceBalanced 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.

• The balanced forces are the forces in equal and opposite directions.

Forces change motion.

• HMM…. Can you see the unbalanced force here?

• HMM…. Can you see the unbalanced force here?

•

Inertia –An object at rest will stay at rest unless acted upon by an outside force.

–Inertia is every objects resistance to change its motion.

Newton’s First LawNewton’s First Law

Greater mass

means

Greater inertia

Greater mass

means

Greater inertia

•Take out a piece of paper

and label it “Inertia Mini

Lab”

•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 accelerationForce=mass x accelerationF=m x aF=m x a

• Or

• a = Force/ mass

• a = F/m

• Or

• a = Force/ mass

• a = F/m

Equation for Newton

•Newton=m x a.•Newton=m x a.

It’s the same as the force equation!

It’s the same as the force equation!

Force and mass determine

acceleration.

Luke! Use the mass times

the 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 2 3

33% 33%33%

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

If you drop a 15kg bowling ball with a Force of 147N, what is it’s

acceleration?

•Acceleration=Force/Mass•a=F/m•a=147kgxm/s/s÷15kg•a= 9.8m/s/s

1 2 3

33% 33%33%

1. 9.8m/s/s

2. 0.1m/s/s

3. 2,205m/s/s

• 0• 0

• 30

• 30

A person throws a baseball at an acceleration of 25m/s/s with

12.5N of Force. What’s the Mass of the ball?

1 2 3

33% 33%33%

1. 312kg

2. .5kg

3. 2kg

•Mass=Force/Acceleration•m=F/a•a=12.5kgxm/s/s÷25m/s/s•a= .5kg

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?

•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?

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 Earth- acceleration 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 velocityMomentum = mass x velocity

• Kg x m/s• Kg x m/s

COLLISIONS

Law of Conservation of Momentum

• The total momentum of the objects that interact does not change.