 Define the following terms  A. Weight  B. Gravity  C. Friction S-33 I can explain the relationship between weight, gravity, and friction

 What does friction normally do to a moving object?  What would be different in the world if there was not friction? S-25 I can describe different kinds of force.

SPS8 Students will determine relationships among force, mass, and motion. b. Apply Newton’s three Laws to everyday situations. c. Relate falling objects to gravitational force. d. Explain the difference in mass and weight. Chapter 12 Newton’s Laws

How do forces affect the motion of an object? What the four main types of friction? How do gravity and air resistance affect a falling object? In what direction does Earth’s gravity act? 12.1 Forces

 Force – a push or a pull on an object  Forces cause changes in velocity  Acceleration - change the objects speed  or direction  Measured  Scale, Force Sensor  Unit – measured in Newton’s (N)  A medium apple will apply a force of about 1 N 12.1 Force 12.1 Forces How do forces affect the motion of an object?

 Forces are vectors so they are drawn using arrows (show magnitude and direction)  Net Force – the overall force acting on an object after all the forces are combined  Balanced forces – the net force is zero, no acceleration  Unbalanced forces – objects accelerate 12.1 Force 12.1 Forces How do forces affect the motion of an object?

 Friction – a force that opposes the motion of objects that touch as they move past each other  Four Types  Static Friction – when objects aren’t moving  Sliding Friction – when objects are sliding past each other 12.1 Force 12.1 Forces What are the four main types of friction

 Rolling Friction – allows movement forward, but not side to side  Fluid Friction – when an object is moving through a fluid ▪ Fluids are liquids or gases – anything that flows ▪ Air resistance is a form of fluid friction 12.1 Force 12.1 Forces What are the four main types of friction

 Gravity – the force of attraction between any two objects with mass  Earth’s gravity points toward the center of the earth – pulls anything with mass  Called weight 12.1 Force 12.1 Forces How does gravity and air resistance affect a falling object

 Name and describe the four types of friction. S-26 I can describe different kinds of force.

 What is the difference between weight and mass. S-27 I can describe different kinds of force.

 When an object is falling, two forces act on it  What do you think they are? ▪ Weight ▪ Air Resistance  Objects will accelerate because of gravity until they reach a terminal velocity – the speed at which the weight and air resistance are equal  For example – terminal speed of a raindrop is about 9 m/s  Human – 76 m/s 12.1 Force 12.1 Forces How does gravity and air resistance affect a falling object Gravity (Weight) Air Resistance

How does Newton’s first law relate change in motion to a zero net force? How does Newton’s second law relate force, mass, and acceleration? How are weight and mass related? 12.2 Newton’s 1 st and 2 nd Laws of Motion

12.1 Force 12.2 Newton’s 1 st & 2 nd Laws How does Newton’s first law relate change in motion to a zero net force  Newton’s First Law of Motion  The state of motion of an object does not change as long as the net force acting on the object is zero  More commonly ▪ An object at rest remains at rest, and an object in motion remains in motion, unless acted on by an outside force.  Sometimes called the law of inertia ▪ Inertia – the tendency of an object to resist a change in its motion

12.1 Force 12.2 Newton’s 1 st & 2 nd Laws How does Newton’s second law relate force, mass, and acceleration  Newton’s Second Law of Motion  The acceleration of an object is equal to the net force acting on it divided by the object’s mass.  F – Force in Newtons  m – mass in kilograms  a – acceleration in m/s 2  Always in the same direction as the net force

12.1 Force 12.2 Newton’s 1 st & 2 nd Laws How does Newton’s second law relate force, mass, and acceleration  Newton’s Second Law of Motion – Practice Problems  A car with a mass of 1000 kg accelerates when the traffic light turns green. If the net force on the car is 4000 N, what is the cars acceleration?  Equation?  Variables?  Filled In Equation?  Answer?

12.1 Force 12.2 Newton’s 1 st & 2 nd Laws How does Newton’s second law relate force, mass, and acceleration  Newton’s Second Law of Motion – Practice Problems  An automobile with a mass of 1200 kg accelerates at a rate of 3.0 m/s2. What is the force acting on the automobile?  Equation?  Variables?  Filled In Equation?  Answer?

12.1 Force 12.2 Newton’s 1 st & 2 nd Laws How does Newton’s second law relate force, mass, and acceleration  Newton’s Second Law of Motion – Practice Problems  A 25 N force accelerates a man on a scooter at 0.5 m/s2. What is the mass of the man and scooter?  Equation?  Variables?  Filled In Equation?  Answer?

12.1 Force 12.2 Newton’s 1 st & 2 nd Laws How are weight and mass related  Weight and Mass  Weight the force of gravity acting on an object  Its mass times acceleration due to gravity  W – Weight in Newtons  m – mass in kilograms  g – 9.80 m/s 2

 How much force must be applied to make a 45 kg kid on a skate board accelerate at 3 m/s 2 ?.  What is the acceleration of a 4000 kg rocket if 30,000 N of force is applied to it? S-28 I can use Newton’s 2 nd Law to calculate quantities.

12.1 Force 12.2 Newton’s 1 st & 2 nd Laws How are weight and mass related  Weight and Mass  Mass is a measurement of the inertia of an object  Weight is a measurement of the force of gravity acting on an object

What is Newton’s third law of motion? 12.3 Newton’s 3 rd Law of Motion and Momentum

12.1 Force 12.3 Newton’s 3 rd Law What is Newton’s third law of motion  Newton’s Third Law  Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first object.  Identify the following action and reaction forces

12.1 Force 12.3 Newton’s 3 rd Law What is Newton’s third law of motion  Newton’s Third Law  Action-Reaction pairs can cause motion  The donkey pushes on the ground, the ground pushes the donkey forward  Does the donkey push the ground backward?  Action-Reaction pairs don’t cancel  They don’t act on the same objects

 Name the action reaction pairs in the following pictures. S-29 What is Newton’s Third Law of Motion.

 A 45 kg duck slams into a wall going at 15 m/s. He comes to a complete stop in 3 s.  A. What is his change is velocity?  B. What is his acceleration?  C. What is the force on the duck?  D. What is the reaction force? S-30 What is Newton’s Third Law of Motion.

What are the four fundamental forces? 12.4 Universal Forces

12.1 Force 12.4 Universal Forces What are the four fundamental forces  Electromagnetic Forces  Associated with charged particles  Electric Force – between two charged particles  Negative and positive  Opposites attract, like repels  Magnetic Force – between other magnets and certain metals

12.1 Force 12.4 Universal Forces What are the four fundamental forces  Strong Nuclear Force  Act to hold the nucleus together  Overcomes repulsion of positive protons with each other  The strongest force over small (tiny, tiny) distances

12.1 Force 12.4 Universal Forces What are the four fundamental forces  Weak Nuclear Force  Involved in certain types of radioactive processes  Active only over distances even smaller than the strong nuclear force

12.1 Force 12.4 Universal Forces What are the four fundamental forces  Gravitational Force  Between any two objects with mass  Depends on the mass and the distance between the objects  Very weak force  Acts over very long distances

 List and briefly describe the 4 fundamental forces. S-31 What are the four fundamental forces?

 A guys is smashed by another guy.  A. If the guy in blue smashes the other guy with a force of 2000 N, and the second guy has a mass of 125kg, what is his acceleration?  B. What is the force felt by the blue guy? S-32 How does Newton’s second law relate force, mass, and acceleration?

We have a Test? S-33