UEQ: How do forces affect the motion of objects? Day 1 Newton’s 1st and 2nd Law
†After Attendance (†EQ Sheet; Concept Map) Place HW on my desk †Pickup a new Essential Question Sheet and an Effects of Force Concept Map Pickup and sign out your computer Log into www.plutonium-239.com Select the Warm-Up link Complete today’s warm-up and submit it Logout and return the computer to the cart 2
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Dynamics: Newton’s Laws of Motion UEQ: How do forces affect the motion of objects? Dynamics: Newton’s Laws of Motion
Review of Concept Map & Units of Chapter 4 UEQ: How do forces affect the motion of objects? Review of Concept Map & Units of Chapter 4 Force Newton’s First Law of Motion Mass Newton’s Second Law of Motion Newton’s Third Law of Motion Weight – the Force of Gravity; and the Normal Force
UEQ: How do forces affect the motion of objects? Units of Chapter 4 Solving Problems with Newton’s Laws: Free-Body Diagrams Applications Involving Friction, Inclines Problem Solving – A General Approach
Equations to Know: Forces UEQ: How do forces affect the motion of objects? Equations to Know: Forces F=ma G=mg f=N
Effects of Forces: Law of Inertia EQ(s): How can forces be measured and quantified? What are the defining characteristics of inertia? Start: Why is it more dangerous to get hit by a car than a snowball? 8
How can forces be measured and quantified? What is a Force? According to Sir Alec Guiness: http://www.youtube.com/watch?v=ukbTFgQ4jxs
How can forces be quantified and measured? A force is a push or pull. An object at rest needs a force to get it moving; a moving object needs a force to change its velocity. The magnitude of a force can be measured using a spring scale.
How can forces be quantified and measured? 4-1 Get To kNow All Forces G: Gravity T: Tension (ex. A tug-of-war rope) N: Normal (ex. The floor below you) A: Applied (ex. Pushing on a door) F: Friction
How can forces be quantified and measured? 4-1 Get To kNow All Forces Standing on the ground Driving at a constant speed Hitting T-ball Tetherball Walking
4-2 Newton’s First Law of Motion What are the defining characteristics of inertia? 4-2 Newton’s First Law of Motion Newton’s first law is often called the law of inertia. Every object continues in its state of rest, or of uniform velocity in a straight line, as long as no net force acts on it.
4-2 Newton’s First Law of Motion What are the defining characteristics of inertia? 4-2 Newton’s First Law of Motion Inertial reference frames: An inertial reference frame is one in which Newton’s first law is valid. This excludes rotating and accelerating frames.
What are the defining characteristics of inertia? 4-3 Mass Mass is the measure of inertia of an object. In the SI system, mass is measured in kilograms. Mass is not weight: Mass is a property of an object. Weight is the force exerted on that object by gravity. If you go to the moon, whose gravitational acceleration is about 1/6 g, you will weigh much less. Your mass, however, will be the same.
Summary How can forces be measured and quantified? What are the defining characteristics of inertia? Summary Answer the Essential Questions. Ticket out the Door: What is the unit of mass? What is another name for Newton’s 1st Law? Which force is pushing up on you? HW (Write down in your Student Planner): No Homework 16
UEQ: How do forces affect the motion of objects? Day 2 Newton’s 2nd Law
After Attendance Place HW on my desk Pickup and sign out your computer Log into www.plutonium-239.com Select the Warm-Up link Complete today’s warm-up and submit it Logout and return the computer to the cart 18
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Newton’s 2nd Law EQ(s): How can you infer the forces on an object from information about its motion? How can you use the summation of forces to calculate the acceleration of an object? Start: What factors determine the force of a punch or kick? 20
How can you infer the forces on an object from information about its motion? How can you use the summation of forces to calculate the acceleration of an object? POWER PUNCH
4-4 Newton’s Second Law of Motion Invisible Forces What We See How can you infer the forces on an object from information about its motion? How can you use the summation of forces to calculate the acceleration of an object? 4-4 Newton’s Second Law of Motion Newton’s second law is the relation between acceleration and force. Acceleration is proportional to force and inversely proportional to mass. (4-1) Cause = Effect Invisible Forces What We See
4-4 Newton’s Second Law of Motion How can you infer the forces on an object from information about its motion? How can you use the summation of forces to calculate the acceleration of an object? 4-4 Newton’s Second Law of Motion Force is a vector, so is true along each coordinate axis. The unit of force in the SI system is the newton (N). Note that the pound is a unit of force, not of mass, and can therefore be equated to newtons but not to kilograms.
4-4 Newton’s Second Law of Motion How can you infer the forces on an object from information about its motion? How can you use the summation of forces to calculate the acceleration of an object? 4-4 Newton’s Second Law of Motion When the net force is balanced, the object does not accelerate. When the net force is unbalanced, the object does accelerate.
Newton’s Second Law Lab How can you infer the forces on an object from information about its motion? How can you use the summation of forces to calculate the acceleration of an object? Newton’s Second Law Lab Work in groups of no more than 4 people. Return all supplies to the counter/cart. 25
How can you infer the forces on an object from information about its motion? How can you use the summation of forces to calculate the acceleration of an object? WebAssign/Lab Time Work on WebAssign Problems 4.1 - 4.2 or Newton’s Second Law - Constant Force Lab Final Copy Criteria State the problem (Ex. Find displacement) Draw a picture/diagram Provide a list or table of all given data (Ex. t = 2 s) Solve the problem symbolically (Ex. v=x/t x = vt) Plug in numbers and units to obtain answer. (Ex. x = (5 m/s)(2 s)= 10 m) Notes about WebAssign: Positive vs. negative answers (Try a negative sign) Look at the final unit (hours or minutes or seconds) 26
Summary Answer the Essential Questions. Ticket out the Door: How can you infer the forces on an object from information about its motion? How can you use the summation of forces to calculate the acceleration of an object? Summary Answer the Essential Questions. Ticket out the Door: What is another name for the summation of forces? What part of Newton’s 2nd Law can we “see”? What forces comprise the summation of forces? HW (Write down in your Student Planner): Newton’s Second Law Lab (Questions and Conclusions) WebAssign Problems 4.1 - 4.2 27
Weight; Normal Force; Frictional Force UEQ: How do forces affect the motion of objects? Day 3 Weight; Normal Force; Frictional Force
After Attendance Place HW on my desk Pickup and sign out your computer Log into www.plutonium-239.com Select the Warm-Up link Complete today’s warm-up and submit it Logout and return the computer to the cart 29
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Newton’s 3rd Law EQ(s): What affects the strength of contact forces? Start: Does the kicker feel more or less force than the person being kicked? Life’s Essential Question: What if it was this guy? 31
4-5 Newton’s Third Law of Motion What affects the strength of contact forces? 4-5 Newton’s Third Law of Motion Any time a force is exerted on an object, that force is caused by another object. Newton’s third law: Whenever one object exerts a force on a second object, the second exerts an equal force in the opposite direction on the first.
4-5 Newton’s Third Law of Motion What affects the strength of contact forces? 4-5 Newton’s Third Law of Motion A key to the correct application of the third law is that the forces are exerted on different objects. Make sure you don’t use them as if they were acting on the same object.
4-6 Weight – the Force of Gravity; and the Normal Force What affects the strength of contact forces? 4-6 Weight – the Force of Gravity; and the Normal Force Weight is the force exerted on an object by gravity. Close to the surface of the Earth, where the gravitational force is nearly constant, the weight is:
4-6 Weight – the Force of Gravity; and the Normal Force What affects the strength of contact forces? 4-6 Weight – the Force of Gravity; and the Normal Force An object at rest must have no net force on it. If it is sitting on a table, the force of gravity is still there; what other force is there? The force exerted perpendicular to a surface is called the normal force. It is exactly as large as needed to balance the force from the object (if the required force gets too big, something breaks!)
4-8 Applications Involving Friction, Inclines What affects the strength of contact forces? 4-8 Applications Involving Friction, Inclines On a microscopic scale, most surfaces are rough. The exact details are not yet known, but the force can be modeled in a simple way. For kinetic – sliding – friction, we write: is the coefficient of kinetic friction, and is different for every pair of surfaces.
4-8 Applications Involving Friction, Inclines What affects the strength of contact forces? 4-8 Applications Involving Friction, Inclines
4-8 Applications Involving Friction, Inclines What affects the strength of contact forces? 4-8 Applications Involving Friction, Inclines Static friction is the frictional force between two surfaces that are not moving along each other. Static friction keeps objects on inclines from sliding, and keeps objects from moving when a force is first applied.
4-8 Applications Involving Friction, Inclines What affects the strength of contact forces? 4-8 Applications Involving Friction, Inclines The static frictional force increases as the applied force increases, until it reaches its maximum. Then the object starts to move, and the kinetic frictional force takes over.
What affects the strength of contact forces? Icy Intersection Watch the motion of the tires: Are they rotating? Why is this important to understanding their motion?
Newton’s 2nd Law - Constant Force Lab What affects the strength of contact forces? Newton’s 2nd Law - Constant Force Lab Work in groups of no more than 4 people. Return all supplies to the counter/cart. 41
What affects the strength of contact forces? WebAssign/Lab Time Work on WebAssign Problems 4.3 - 4.5 or Newton’s Second Law - Constant Force Lab Final Copy Criteria State the problem (Ex. Find displacement) Draw a picture/diagram Provide a list or table of all given data (Ex. t = 2 s) Solve the problem symbolically (Ex. v=x/t x = vt) Plug in numbers and units to obtain answer. (Ex. x = (5 m/s)(2 s)= 10 m) Notes about WebAssign: Positive vs. negative answers (Try a negative sign) Look at the final unit (hours or minutes or seconds) 42
What affects the strength of contact forces? Summary Answer the Essential Questions. Ticket out the Door: What is the formula used to calculate weight? The force of gravity pull on an object is also known as ________. What is the formula for the force of friction? HW (Write down in your Student Planner): Newton’s Second Law - Constant Force Lab (Questions and Conclusions) WebAssign Problems 4.3 - 4.5 43
Free Body Diagrams; Inclined Planes; Problem Solving UEQ: How do forces affect the motion of objects? Day 4 Free Body Diagrams; Inclined Planes; Problem Solving
After Attendance Place HW on my desk Pickup and sign out your computer Log into www.plutonium-239.com Select the Warm-Up link Complete today’s warm-up and submit it Logout and return the computer to the cart 45
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Free Body Diagrams EQ(s): How do you use vectors to draw a free body diagram? How do you use a free body diagram to determine the net force on an object? Start: What forces are acting on the person being kicked? 47
4-7 Solving Problems with Newton’s Laws – Free-Body Diagrams How do you use vectors to draw a free body diagram? How do you use a free body diagram to determine the net force on an object? 4-7 Solving Problems with Newton’s Laws – Free-Body Diagrams Draw a sketch. For one object, draw a free-body diagram, showing all the forces acting on the object. Make the magnitudes and directions as accurate as you can. Label each force. If there are multiple objects, draw a separate diagram for each one. Resolve vectors into components. Apply Newton’s second law to each component. Solve.
4-7 Solving Problems with Newton’s Laws – Free-Body Diagrams How do you use vectors to draw a free body diagram? How do you use a free body diagram to determine the net force on an object? 4-7 Solving Problems with Newton’s Laws – Free-Body Diagrams When a cord or rope pulls on an object, it is said to be under tension, and the force it exerts is called a tension force.
4-8 Applications Involving Friction, Inclines How do you use vectors to draw a free body diagram? How do you use a free body diagram to determine the net force on an object? 4-8 Applications Involving Friction, Inclines An object sliding down an incline has three forces acting on it: the normal force, gravity, and the frictional force. The normal force is always perpendicular to the surface. The friction force is parallel to it. The gravitational force points down. If the object is at rest, the forces are the same except that we use the static frictional force, and the sum of the forces is zero.
4-9 Problem Solving – A General Approach How do you use vectors to draw a free body diagram? How do you use a free body diagram to determine the net force on an object? 4-9 Problem Solving – A General Approach Read the problem carefully; then read it again. Draw a sketch, and then a free-body diagram. Choose a convenient coordinate system. List the known and unknown quantities; find relationships between the knowns and the unknowns. Estimate the answer. Solve the problem without putting in any numbers (algebraically); once you are satisfied, put the numbers in. Keep track of dimensions. Make sure your answer is reasonable.
Newton’s 2nd Law - Constant Force Lab How do you use vectors to draw a free body diagram? How do you use a free body diagram to determine the net force on an object? Newton’s 2nd Law - Constant Force Lab Work in groups of no more than 4 people. Return all supplies to the counter/cart. 52
How do you use vectors to draw a free body diagram? How do you use a free body diagram to determine the net force on an object? WebAssign/Lab Time Work on WebAssign Problems 4.1 - 4.22 or Newton’s Second Law - Constant Force Lab Final Copy Criteria State the problem (Ex. Find displacement) Draw a picture/diagram Provide a list or table of all given data (Ex. t = 2 s) Solve the problem symbolically (Ex. v=x/t x = vt) Plug in numbers and units to obtain answer. (Ex. x = (5 m/s)(2 s)= 10 m) Notes about WebAssign: Positive vs. negative answers (Try a negative sign) Look at the final unit (hours or minutes or seconds) 53
How do you use vectors to draw a free body diagram? How do you use a free body diagram to determine the net force on an object? Summary Answer the Essential Questions. Ticket out the Door: Draw a FBD for m1. (3 Forces) Draw a FBD for m2. (2 Forces) Write the individual Fx for m1. HW (Write down in your Student Planner): Newton’s Second Law - Constant Force Lab (Questions and Conclusions) WebAssign Problems 4.1 - 4.22 54
UEQ: How do forces affect the motion of objects? Day 5 Work Day
After Attendance Place HW on my desk Pickup and sign out your computer Log into www.plutonium-239.com Select the Warm-Up link Complete today’s warm-up and submit it Logout and return the computer to the cart 56
Feed Back for Google Docs Was anything confusing on google docs? Noteworthy Student Responses
Newton’s 2nd Law - Constant Force Lab How do you use vectors to draw a free body diagram? How do you use a free body diagram to determine the net force on an object? Newton’s 2nd Law - Constant Force Lab Work in groups of no more than 4 people. Return all supplies to the counter/cart. 58
How do you use vectors to draw a free body diagram? How do you use a free body diagram to determine the net force on an object? WebAssign/Lab Time Work on WebAssign Problems 4.1 - 4.22 or Newton’s Second Law - Constant Force Lab Final Copy Criteria State the problem (Ex. Find displacement) Draw a picture/diagram Provide a list or table of all given data (Ex. t = 2 s) Solve the problem symbolically (Ex. v=x/t x = vt) Plug in numbers and units to obtain answer. (Ex. x = (5 m/s)(2 s)= 10 m) Notes about WebAssign: Positive vs. negative answers (Try a negative sign) Look at the final unit (hours or minutes or seconds) 59
How do you use vectors to draw a free body diagram? How do you use a free body diagram to determine the net force on an object? Summary Answer the Essential Questions. Ticket out the Door: Not Applicable HW: Newton’s Second Law - Constant Force Lab (Questions and Conclusions) WebAssign Problems 4.1 - 4.22 60
UEQ: How do forces affect the motion of objects? Day 6 Work Day #2
After Attendance Place HW on my desk Pickup and sign out your computer Log into www.plutonium-239.com Select the Warm-Up link Complete today’s warm-up and submit it Logout and return the computer to the cart 62
Feed Back for Google Docs Was anything confusing on google docs? Noteworthy Student Responses
Newton’s 2nd Law - Constant Force Lab How do you use vectors to draw a free body diagram? How do you use a free body diagram to determine the net force on an object? Newton’s 2nd Law - Constant Force Lab Work in groups of no more than 4 people. Return all supplies to the counter/cart. 64
How do you use vectors to draw a free body diagram? How do you use a free body diagram to determine the net force on an object? WebAssign/Lab Time Work on WebAssign Problems 4.1 - 4.22 or Newton’s Second Law - Constant Force Lab Final Copy Criteria State the problem (Ex. Find displacement) Draw a picture/diagram Provide a list or table of all given data (Ex. t = 2 s) Solve the problem symbolically (Ex. v=x/t x = vt) Plug in numbers and units to obtain answer. (Ex. x = (5 m/s)(2 s)= 10 m) Notes about WebAssign: Positive vs. negative answers (Try a negative sign) Look at the final unit (hours or minutes or seconds) 65
How do you use vectors to draw a free body diagram? How do you use a free body diagram to determine the net force on an object? Summary Answer the Essential Questions. Ticket out the Door: Not Applicable HW: Newton’s Second Law - Constant Force Lab (Questions and Conclusions) WebAssign Problems 4.1 - 4.22 66
Day 7 Summary/Work Day
After Attendance Place HW on my desk Pickup and sign out your computer Log into www.plutonium-239.com Select the Warm-Up link Complete today’s warm-up and submit it Logout and return the computer to the cart 68
Feed Back for Google Docs Was anything confusing on google docs? Noteworthy Student Responses
Summary of the Effects of Force UEQ: How do forces affect the motion of objects? Summary of the Effects of Force Newton’s first law: If the net force on an object is zero, it will remain either at rest or moving in a straight line at constant speed. Newton’s second law: Newton’s third law: Weight is the gravitational force on an object. The frictional force can be written: (kinetic friction) or (static friction) Free-body diagrams are essential for problem-solving
†Effects of Force Essential Questions UEQ: How do forces affect the motion of objects? †Effects of Force Essential Questions What are the defining characteristics of inertia? How can forces be quantified and measured? How can you use the summation of forces to calculate the acceleration of an object? How can you infer the forces on an object from information about its motion? What affects the strength of the contact forces? How do you use vectors to draw a free body diagram? How do you use a free body diagram to determine the summation of forces on an object? †Answer these before the test.
Newton’s 2nd Law - Constant Force Lab UEQ: How do forces affect the motion of objects? Newton’s 2nd Law - Constant Force Lab Work in groups of no more than 4 people. Return all supplies to the counter/cart. 72
†EQ/WebAssign/Lab Time UEQ: How do forces affect the motion of objects? †EQ/WebAssign/Lab Time †Answer the Essential Questions Work on WebAssign Problems 4.1 - 4.22 or Newton’s Second Law - Constant Force Lab Final Copy Criteria State the problem (Ex. Find displacement) Draw a picture/diagram Provide a list or table of all given data (Ex. t = 2 s) Solve the problem symbolically (Ex. v=x/t x = vt) Plug in numbers and units to obtain answer. (Ex. x = (5 m/s)(2 s)= 10 m) Notes about WebAssign: Positive vs. negative answers (Try a negative sign) Look at the final unit (hours or minutes or seconds) 73
UEQ: How do forces affect the motion of objects? Summary Ticket out the Door: Write down two questions and their answer for the test tomorrow and turn it in. One conceptual problem One mathematical problem HW (Write down in your Student Planner): Answer the Essential Questions Newton’s Second Law - Constant Force Lab (Questions and Conclusions) WebAssign Problems 4.1 - 4.22 WebAssign Final Copy 74
Day 8: Test Effects of Force
UEQ: How do forces affect the motion of objects? †After Attendance Place HW on my desk (in Reverse Alphabetical Order): WebAssign Final Copy Essential Questions Laboratory Assignment(s) Pickup the following: Chapter 5 Vocabulary Acceleration Scantron Sheet Fill in the following on the scantron sheet front: Name: Write your name on it!! Subject: PIM Test: EOF Date: S10 Period: Block 2 76
UEQ: How do forces affect the motion of objects? †Effects of Force Test Do not write on Part I (the scantron questions) Put your name on Part II and complete it Verify any corrections below that have made before submitting your test. Complete the Chapter 5 Vocabulary Acceleration Test Corrections Question
UEQ: How do forces affect the motion of objects? Summary Ticket out the Door: Turn in the Effects of Force Test HW: Chapter 5 Vocabulary Acceleration 78
4-5 Newton’s Third Law of Motion Rocket propulsion can also be explained using Newton’s third law: hot gases from combustion spew out of the tail of the rocket at high speeds. The reaction force is what propels the rocket. Note that the rocket does not need anything to “push” against.
4-5 Newton’s Third Law of Motion Helpful notation: the first subscript is the object that the force is being exerted on; the second is the source. This need not be done indefinitely, but is a good idea until you get used to dealing with these forces. (4-2)