Chapter Menu Chapter Introduction Lesson 1Lesson 1Newton’s First Law Lesson 2Lesson 2Gravity and Friction Lesson 3Lesson 3Newton’s Second Law Lesson 4Lesson 4Newton’s Third Law Chapter Wrap-Up

Chapter Introduction How do forces change the motion of objects?

Chapter Introduction What do you think? Before you begin, decide if you agree or disagree with each of these statements. As you view this presentation, see if you change your mind about any of the statements.

Chapter Introduction 1.You pull on objects around you with the force of gravity. 2.Friction can act between two unmoving, touching surfaces. 3.Forces acting on an object cannot be added. Do you agree or disagree?

Chapter Introduction 4.A moving object will stop if no forces act on it. 5.When an object’s speed increases, the object accelerates. 6.If an object’s mass increases, its acceleration also increases if the net force acting on the object stays the same. Do you agree or disagree?

Chapter Introduction 7.If objects collide, the object with more mass applies more force. 8.Momentum is a measure of how hard it is to stop a moving object. Do you agree or disagree?

Lesson 1 Reading Guide - Vocab force contact force noncontact force gravity Gravity and Friction mass weight friction

Lesson 2-2 According to Newton’s first law of motion, an object at rest will stay at rest, and an object in motion will continue moving unless acted upon by an unbalanced force.Newton’s first law of motion Newton’s First Law of Motion

Lesson 1-1 A push or a pull is called a force.force An object or a person can apply a force to another object or person. Types of Forces force from Latin fortis, means “strong”

Lesson 2-1 Balanced forces forces on an object that are equal in size and opposite in direction. Net force = 0 Do not cause motion.Balanced forces Forces that combine and form a net force >zero are unbalanced forces. Cause motion.unbalanced forces Identifying Forces (cont.)

Lesson 2-2 Balanced forces acting on an object do not change the object’s speed and direction. Newton’s first law of motion only applies to balanced forces acting on an object. When unbalanced forces act on an object, the object’s velocity changes. Newton’s First Law of Motion (cont.)

Lesson 1-1 A contact force is a force that is applied when two objects touch.contact force A force that one object can apply to another object without touching it is a noncontact force. noncontact force Types of Forces (cont.)

Lesson 1-1 Can you think of an example of a contact force? Can you think of an example of a noncontact force? Types of Forces (cont.)

Contact: Pushing a book off of a table Noncontact: Gravity or magnetic forces

Agree or Disagree: A moving object will stop if there are no forces acting on it? Think About it: If you kick a soccer ball across a field will it go on forever? What forces will cause it to stop? If there where no forces acting on it (friction, gravity, walls, people) would the soccer ball continue to move?

Lesson 2-1 The sum of all the forces acting on an object is the net force.net force The net force depends on the directions of the forces applied to an object. Because forces have direction, you have to specify a reference direction when you add forces. Identifying Forces

Lesson 2-1 When forces act in opposite direction on an object, the net force is still the sum of the forces. The net force is the sum of the positive and negative forces. Identifying Forces (cont.)

Inertia- the tendency of an object to resist changes in motion Examples… An object with less mass has less inertia and an object with more mass has more inertia Can you think of any examples?

Lesson 1-1 Is it easier to throw a baseball or a bowling ball? Explain why. Explain which has greater inertia: a jet plane sitting on the runway or a speeding car? Types of Forces (cont.)

Lesson 2 - VS Unbalanced forces cause an object to move. According to Newton’s first law of motion, if the net force on an object is zero, the object’s velocity does not change. Inertia is a property that resists a change in the motion of an object.

Lesson 3 - VS Unbalanced forces cause an object to speed up, slow down, or change direction.

Lesson 1 Reading Guide - KC Friction and gravity are two forces that can change the motion of an object. What is the law of universal gravitation? How does friction affect the motion of two objects sliding past each other? Gravity and Friction 2

Lesson 1-3 Friction is a force that opposes the movement between two touching surfaces.Friction There are several types of friction. static friction sliding friction fluid friction Friction

Lesson 1-3 What causes friction between surfaces? –When the microscopic dips and bumps on one surface catch the dips and bumps on another surface, the microscopic roughness slows sliding. Friction (cont.)

Lesson 1-3 Static friction prevents surfaces from sliding past each other. Up to a limit, the strength of static friction changes to match the applied force. Sliding friction opposes the motion of surfaces sliding past each other. Friction (cont.)

Fluid friction is friction between a surface and a fluid—any material, such as water or air, that flows. Fluid friction between a surface and air is air resistance. The greater the surface area of an object, the more air resistance it will experience. Lesson 1-3 Friction (cont.)

Lesson 1-3 Friction (cont.) How does friction affect the motion of two objects sliding past each other?

Lesson 1-3 Lubricants decrease friction and with less friction, it is easier for surfaces to slide past each other. What reduces friction between a door and a hinge? What reduced friction between two bones in a joint? Reducing Friction

Increasing Friction –How would you increase the friction between your foot and the ice on the sidewalk?

Lesson 1-2 Gravity is an attractive force that exists between all objects that have mass.Gravity Objects fall to the ground because Earth exerts gravity on them. Earth’s gravitational force pulls objects towards Earth’s surface. Mass is the amount of matter in an object.Mass Mass is often measured in kilograms (kg). What is gravity?

Lesson 1-2 Sir Isaac Newton developed the law of universal gravitation in the late 1600s. The law of universal gravitation states that all objects are attracted to each other by a gravitational force. What is gravity? (cont.)

Lesson 1-2 The strength of force depends on the mass of each object and the distance between them. When the mass of one or both objects increases, the gravitational force between them also increases. What is gravity? (cont.)

Lesson 1-2 Weight is the gravitational force exerted on an object.Weight Near Earth’s surface, an object’s weight is the gravitational force exerted on the object by Earth. Because weight is a force, it is measured in newtons. What is gravity? (cont.)

Lesson 1-2 An object’s weight is proportional to its mass. Near Earth’s surface, the weight of an object in newtons is about ten times (9.8x) its mass in kilograms. What is gravity? (cont.)

Lesson 2-3 For an object to start moving, a force greater than static friction must be applied to it. To keep an object in motion, a force at least as strong as friction must be applied continuously. Objects stop moving because friction or another force acts on them. Why do objects stop moving?

Lesson 1 - VS Gravity is an attractive force that acts between any two objects that have mass. The attraction is stronger for objects with greater mass.

Friction can reduce the speed of objects sliding past each other. Air resistance is a type of fluid friction that slows the speed of a falling object.

LESSON 1 – LR1 A.contact force B.gravity C.mass D.weight Which refers to gravitational force exerted on an object?

LESSON 1 – LR2 A.gravitational force B.length C.mass D.noncontact force Which is proportional to an object’s weight?

Lesson 1 - Now 1.You pull on objects around you with the force of gravity. 2.Friction can act between two unmoving, touching surfaces. Do you agree or disagree?

Lesson 1 – LR2 A.Gravity B.Newton C.Force D.Motion A push or a pull is called a?

Lesson 1 – LR3 A.net force B.lubricant C.gravity D.friction Which is a force that opposes the movement between two touching surfaces?

Lesson 2 – LR1 A.balanced forces B.inertia C.net force D.unbalanced forces Which refers to forces that combine and form a net force that is greater than zero?

Lesson 2 – LR2 A.friction B.inertia C.unbalanced forces D.velocity Which could cause an object to stop moving?

Lesson 2 – LR3 A.zero B.one C.equal D.balanced When equal forces act on an object in opposite directions, what is the net force on the object?

Lesson 2 - Now 2. Friction can act between two unmoving, touching surfaces. Agree 3.Forces acting on an object cannot be added. Disagree Do you agree or disagree?

Lesson 3 Reading Guide - KC What is Newton’s second law of motion? How does centripetal force affect circular motion? Newton’s Second Law

Lesson 3-1 Forces change an object’s motion by changing its speed, its direction, or both its speed and its direction. Velocity is speed in a certain direction. Only unbalanced forces change an object’s velocity. Unbalanced forces make an object accelerate by changing its speed, its direction, or both. How do forces change motion?

Lesson 3-1 Acceleration is a measure of how much the velocity of an object changes in a unit of time.Acceleration An object accelerates when its velocity changes as a result of increasing speed, decreasing speed, or a change in direction. Acceleration—Changes in Velocity

Lesson 3-1 When unbalanced forces act on an object at rest, the object begins moving –in the same direction of the net force. If the net force acting on a moving object is in the same direction that the object is moving –the object will speed up. If the direction of the net force on an object is opposite to the direction the object moves –the object slows down. How do forces change motion? (cont.)

Lesson 3-2 According to Newton’s second law of motion, the acceleration of an object is equal to the net force acting on the object divided by the object’s mass.Newton’s second law of motion Newton’s Second Law of Motion

As the mass of an object increases the amount of force required to move the object: –Increases As the force applied to an object increases the acceleration of the object will: –Increase

Lesson 3-2 Force = Mass x Acceleration Acceleration is expressed in meters per second squared (m/s 2 ), Mass in kilograms (kg), Force in Newtons (N). Newton’s Second Law of Motion (cont.)

Lesson 3 – LR1 A.acceleration B.centripetal force C.inertia D.velocity Which term refers to speed in a certain direction?

Lesson 3 – LR3 A.inertia B.acceleration C.circulation motion D.centripetal force Which refers to a change in velocity over time?

Lesson 3 - Now 5.When an object’s speed increases, the object accelerates. Agree 6.If an object’s mass increases, its acceleration also increases if the net force acting on the object stays the same. Disagree Do you agree or disagree?

Lesson 1-1 The SI unit for force is the newton (N). Arrows can be used to show both the strength and direction of force.

Lesson 4 Reading Guide - KC What is Newton’s third law of motion? Why don’t the forces in a force pair cancel each other? What is the law of conservation of momentum? Newton’s Third Law

Lesson 4 Reading Guide - Vocab Newton’s third law of motion force pair momentum law of conservation of momentum Newton’s Third Law

Lesson 4-2 According to Newton’s third law of motion, for every action there is an equal and opposite reaction.Newton’s third law of motion Ex: When you jump on a trampoline you exert a downward force on the trampoline and it exerts an upward force on you. –The more force you use to jump down with, the higher you bounce back into the air. Newton’s Third Law of Motion

Lesson 4-2 A force pair is the forces two objects apply to each other.force pair In a force pair, one force is called the action force and the other force is called the reaction force. Newton’s Third Law of Motion (cont.)

Lesson 4-3 When you push against an object, the force you apply is called the action force. The force applied by the object back against you is called the reaction force. Using Newton’s Third Law of Motion

Can you think of some examples that illustrate Newton’s 3 rd law? –Parachute- downward force of you falling, upward force of air –Swimming pool- backward force of you pushing, forward force of you moving away from wall

If the forces of a force pair always act in opposite directions and are always the same strength, they do not cancel each other out because each force acts on a different object. STOP HERE

Discuss: What is momentum? Which object will have the most momentum (tennis ball, wiffle ball, or a lacrosse ball?)

Lesson 4-4 MomentumMomentum is a measure of how hard it is to stop a moving object. Momentum momentum from Latin momentum, means “movement, impulse”

Read through the lab Answer the pre-lab questions What safety precautions should we take while completing this lab

Lesson 4-4 Momentum (cont.) Momentum is the product of an object’s mass and velocity.

Lesson 4-4

Momentum (cont.) An object’s momentum is in the same direction as its velocity. According to Newton’s first law, if the net force on an object is zero, neither its velocity nor its momentum change. Because momentum is the product of mass and velocity, the force on an object equals its change in momentum.

Lesson 4-5 According to the law of conservation of momentum, the total momentum of a group of objects stays the same unless outside forces such as friction act on the objects.law of conservation of momentum Conservation of Momentum What is the law of conservation of momentum?

Lesson 4-5 When colliding objects bounce off each other, it is an elastic collision. If objects collide and stick together, the collision is inelastic. No matter the type of collision, the total momentum will be the same before and after the collision. Conservation of Momentum (cont.)

Lesson 4 - VS Newton’s third law of motion describes the force pair between two objects. For every action force, there is a reaction force that is equal in strength but opposite in direction. In any collision, momentum is transferred from one object to another.

Lesson 4 – LR1 A.Newton’s third law of motion B.Newton’s second law of motion C.Newton’s first law of motion D.law of conservation of momentum Which law explains that every force has a reaction force in the opposite direction?

Lesson 4 – LR2 A.velocity B.momentum C.inertia D.elastic collision Which is a measure of how hard it is to stop a moving object?

Lesson 4 – LR3 A.velocity B.momentum C.force pair D.collision Which refers to the forces two objects apply to each other?

Lesson 4 - Now 7.If objects collide, the object with more mass applies more force. 8.Momentum is a measure of how hard it is to stop a moving object. Do you agree or disagree?

Chapter Review Menu Key Concept Summary Interactive Concept Map Chapter Review Standardized Test Practice

The BIG Idea An object’s motion changes if a net force acts on the object.

Key Concepts 1 Friction is a contact force. Magnetism is a noncontact force. The law of universal gravitation states that all objects are attracted to each other by gravity. Friction can stop or slow down objects sliding past each other. Lesson 1: Gravity and Friction

Key Concepts 2 Lesson 2: Newton’s First Law An object’s motion can only be changed by unbalanced forces. According to Newton’s first law of motion, the motion of an object is not changed by balanced forces acting on it. Inertia is the tendency of an object to resist a change in its motion.

Key Concepts 3 According to Newton’s second law of motion, an object’s acceleration is the net force on the object divided by its mass. In circular motion, a centripetal force pulls an object toward the center of the curve. Lesson 3: Newton’s Second Law

Key Concepts 4 Newton’s third law of motion states that when one object applies a force on another, the second object applies an equal force in the opposite direction on the first object. The forces of a force pair do not cancel because they act on different objects. According to the law of conservation of momentum, momentum is conserved during a collision unless an outside force acts on the colliding objects. Lesson 4: Newton’s Third Law

Chapter Review – MC1 A.weight B.mass C.inertia D.gravity Which term refers to the amount of matter in an object?

Chapter Review – MC2 A.contact B.gravity C.mass D.noncontact Which refers to a force that is applied when two objects touch?

Chapter Review – MC3 A.unbalanced B.terminal C.centripetal D.balanced Which term refers to forces that combine with a net force of zero?

Chapter Review – MC4 A.velocity B.terminal velocity C.net force D.inertia The tendency of an object to resist a change in its motion is called what?

Chapter Review – MC5 A.Newton’s third law of motion B.Newton’s second law of motion C.Newton’s first law of motion D.law of conservation of momentum Which law states that the total momentum of a group of objects stays the same unless outside forces act on the objects?

Chapter Review – STP1 A.weight B.noncontact C.inertia D.contact Which term refers to a force that one object can apply to another without touching?

Chapter Review – STP2 A.contact B.gravitational C.noncontact D.static Which describes the magnetic force?

Chapter Review – STP3 A.unbalanced B.proportional C.noncontact D.negative Which describes the net force of different forces acting in the same direction?

Chapter Review – STP4 A.stops B.speeds up C.slows down D.changes direction If the net force acting on a moving object is in the direction that the object is moving, the object does what?

Chapter Review – STP5 Which refers to the collision of objects that bounce off each other? A.elastic B.friction C.inelastic D.inertia