Ch. 3 ForcesCh. 3 Forces

3.1 Newton’s Second Law3.1 Newton’s Second Law

3.2 Gravity3.2 Gravity

3.3 The Third Law of Motion3.3 The Third Law of Motion

Newton’s Second LawNewton’s Second Law

• Increase Force=Increase AccelerationIncrease Force=Increase Acceleration• Increase Mass=Increase ForceIncrease Mass=Increase Force

F= maF= ma

• A one-eyed kitty is being pulled by a A one-eyed kitty is being pulled by a car at an acceleration of 2.0 m/scar at an acceleration of 2.0 m/s22. . What is the mass of the kitty cat if the What is the mass of the kitty cat if the net force on the kitty is 1000 N?net force on the kitty is 1000 N?

FrictionFriction

• Inertia-in motion, stays in motion? Inertia-in motion, stays in motion? Impossible-Friction (air resistance). Impossible-Friction (air resistance). Opposing motion of an object. Opposing motion of an object.

Terminal Velocity:Terminal Velocity:– Downward force – Gravity Downward force – Gravity – Upward force- Air resistanceUpward force- Air resistance

• BALANCE OUT- Net Force= 0 BALANCE OUT- Net Force= 0 • NO more accelerationNO more acceleration

3.2 Gravity3.2 Gravity

• Attractive force b/t two objectsAttractive force b/t two objects• Depends on MASS and DISTANCEDepends on MASS and DISTANCE

The Law of Universal GravitationThe Law of Universal Gravitation– Gravity b/t two objects decrease as the distance Gravity b/t two objects decrease as the distance

increases. increases.

Force of Earth’s GravityForce of Earth’s GravityF=mgF=mg

Weight EquationWeight Equation W=mgW=mg

CalculationsCalculations

1.1. On Earth, what is the weight of a On Earth, what is the weight of a killer whale that has a mass of 200 killer whale that has a mass of 200 kg?kg?

2.2. Find the acceleration of gravity on Find the acceleration of gravity on Uranus, if a person has a mass of 60 Uranus, if a person has a mass of 60 kg, and a weight of 200 N. kg, and a weight of 200 N.

3.3. Find the force exerted by a rope on Find the force exerted by a rope on a 10 kg. Mass that is hanging from a 10 kg. Mass that is hanging from the rope?the rope?

Projectile MotionProjectile Motion

• Horizontal and Vertical MotionHorizontal and Vertical Motion

Centripetal ForceCentripetal Force

• Acceleration toward the center of a Acceleration toward the center of a circular path.circular path.

3.3 The Third Law of 3.3 The Third Law of MotionMotion

To every action there is an To every action there is an equal and opposite reaction.equal and opposite reaction.

Momentum EquationMomentum Equation

p=mvp=mv

-Amount of force to -Amount of force to

change is motionchange is motion

CalculationsCalculations

1. What is the momentum of a really fast 1. What is the momentum of a really fast and fat cheetah with a mass of 1,000 kg and fat cheetah with a mass of 1,000 kg traveling at a speed of 28 m/s?traveling at a speed of 28 m/s?

2. A baseball has a momentum of 6.0 kg 2. A baseball has a momentum of 6.0 kg m/s. If the mass of the baseball is 0.15 m/s. If the mass of the baseball is 0.15 kg. What is the speed of the baseball?kg. What is the speed of the baseball?

3. What is the mass of a donkey walking 3. What is the mass of a donkey walking at a speed of 1.0 m/s if the donkey’s at a speed of 1.0 m/s if the donkey’s momentum is 50 kg m/s?momentum is 50 kg m/s?

HomeworkHomework

Pg 834Pg 834

#25-37#25-37