Monday, November 18, 2013

Physics

Warm UpA ball travels 50 meters to the west in 20 seconds.

Find the speed of the ball. Find the velocity of the

ball.

Standards: Students know Newton’s 2nd Law

Objective: SWBAT draw free body diagrams

HomeworkP.3 #F6P.5,6 Finish Graphing & Problem Solving Worksheets and turn in tomorrow. Agenda

1. Warm Up2. P.3 Turn in Graphing &

Problem Solving Worksheets3. Force Stations Lab4. P.5,6 Test

Tuesday, November 19, 2013

Physics

Warm Up Find the acceleration of a car that speeds up from

rest to 10 m/s in 5s?Standards: 1c Newton’s 2nd Law of Motion

Objective: SWBAT create free body diagrams of various physical situations.

Homework#F6 P.4

Agenda1. Warm Up2. P.2 Take Test3. P.4 Free Body

Diagram Mini-Lecture

4. Force Stations: Elaborate Section

Wednesday, November 20, 2013

Physics

Warm UpA cart rolls across a table with

an applied Force of 10N, a frictional force of 5N, no air

resistance, and a mass of 2kg. It’s acceleration is unknown. draw a free body diagram for

this situation.

Homework#F6

Standards: 1.c newton’s 2nd law.

Learning Objective: SWBAT create free body diagrams

Agenda: 1. Warm Up2. Continue working on Force

Stations Lab3. Practice Free body diagrams

Thursday, November 21, 2013

Physics

Warm UpDraw a Free Body Diagram for a car skidding to a stop.

Standards: : 1c Newton’s 2nd Law of Motion

Learning Objective: SWBAT solve problems using Free Body Diagrams

Homework#F7Finish Force Stations labFBD Quiz 6 Friday

Agenda: 1. Warm Up2. P.6,P.7Finish Force Stations Lab3. P.3 FBD Problem Solving: Guided

Practice4. P.3 Solving Free Body Diagram

Problems.

Friday, November 22, 2013

Physics

Standards: 1c Newton’s 2nd Law of Motion

Learning Objective: SWBAT solve problems using free body diagrams. Agenda: 1. Warm Up2. Review HW & Collect Labs3. Quiz4. FBD practice.

Homework#F7&8 p.6,7

Warm UpCreate a free body diagram of a car driving down a hill

where friction & air resistance will affect the

car’s motion.

Symbols, units and equations Study Guide

Equations:

Constant Velocity

Constant Acceleration

1.

2.

The Two equations of Motion The Two equations of Motion for Falling Objects

ag=-9.8m/s2

Forces

Symbol Units

t s

v m/s

a m/s2

F kgm/s2 or N

Δx m

Modeling the Graphing Process

Step One – label each axis with the symbol and the units being represented by the graph.

1st column x-axis, 2nd column y axisStep Two – Create your x and y axis scales. To create a scale(your numbering system on the graph) look at your smallest and largest data points. Then pick a number sequence (ex. 1,2,3,4 or 2,4,6,8) that will allow all of the points to fit on your graph. Step Three – Plot the Points. Step Four – Make a best fine line. It has to be straight and you need to make it go through the center or through the average of your points. See board for more explanation.Step Five – Find the slope of the graph. Step Six (Honors Only) – Find the equation of the graph by substituting your data into the formula y=mx+b

Physics Problem Solving ProcessStep 1: Read the problem twice. Answer: Is the object in the problem traveling at some average or constant speed or is the speed changing or acceleratingStep 2: Look at the group of equations that applies to your situation: Constant Velocity or Acceleration. Then begin to write down the givens and pick their symbols based on the symbols you find in the equations.Step 3: Draw a diagram using the conventions we’ve learned. Be sure to represent all of the givens in your diagram. Step 4: Next pick your equation. The equation should only have one symbol that you don’t know. If it has more than one either pick a different equation with only one, or you may need to think about using another equation in addition. Step 5: Use the equation/s that you’ve picked, plug in the givens (don’t forget to include units) and solve for your unknown.

Step 1: Read the problem twice. Answer: Is the object in the problem traveling at some average or constant speed or is the speed changing or acceleratingStep 2: Look at the group of equations that applies to your situation: Constant Velocity or Acceleration. Then begin to write down the givens and pick their symbols based on the symbols you find in the equations.Step 3: Draw a diagram using the conventions we’ve learned. Be sure to represent all of the givens in your diagram. Step 4: Next pick your equation. The equation should only have one symbol that you don’t know. If it has more than one either pick a different equation with only one, or you may need to think about using another equation in addition. Step 5: Use the equation/s that you’ve picked, plug in the givens (don’t forget to include units) and solve for your unknown.

Physics Problem Solving Process

HW: #F6

*** Extra Credit:After you create each free body diagram, use your free body diagram to make an Fnet=ma equation in the x direction and in the y direction like we did during the Explain portion of the lesson.

Ex

``` `

FN

Fg

FAPFFFAR

Fnetx=Fap-Ff-FAR=macar-x-direction

Fnety=FN-Fg=macar y-direction

Force Stations

• Objective: Gain an introduction to free-body diagrams (FBDs), and create accurate FBDs of physical systems at stations around room.

• Engage• Watch discovery channel video clip on the physics of skydiving (~3 min.):

http:/www.youtube.com/watch?v=ur40O6nQHsw . • Explore• Students rotate around force stations in the room and explore each system ~16 min

o Identify the Labeled Stationo Explore each station: 2 minutes, identify all the forces acting on the object, and draw all the forces on the object.

1. Object at rest on table2. Cart rolling across table3. Object hanging by string4. Object hanging by two strings at an angle to each other5. Ball rolling down ramp6. Object stationary on ramp7. Ball falling through air8. Coffee filters falling through air

• Explain• Mini-lecture on FBDs (Free Body Diagrams) ~5 min• Students revise any force station FBD that is incorrect.• Students finish guided practice problem. • Elaborate• Using magazines provided in class, cut out a picture that shows an interesting physical

scenario. Then students create FBD for one or multiple objects in the cutout picture.• Evaluate• “Free-Body Exercises: Linear Motion” #F6

For the full 10 pts of credit requires full completion of explore, explain, elaborate, and evaluate sections. Evaluate is Homework worth 10 points.

Free Body Diagrams

What are they? – These are diagrams similar to the one’s we are used to drawing, but with one major exception. You only put Forces on them.

Why do we make them?1. They help us solve

problems involving multiple forces.

2. Looking at the diagram to the right. Fnetx=Fap-Ff-FAR

Fnety=FN-Fg

``` `

FN

Fg

FAPFFFAR

When do we make them?Remember Fnet=ma? You create a free body diagram to help you find the Fnet portion of this equation.

Fnetx=Fap-Ff-FAR=macar-x-direction

Fnety=FN-Fg=macar y-direction

Question: If the car has a 2000 kg mass, its applied force is 10,000 N, friction is 1500 N, and Air Resistance is 1000 N, find the car’s acceleration and the *Normal Force acting on the car?

Free Body Diagrams #F7For each problem:a. Draw a Free Body Diagram of the problem. b. Make an equation for Net Force in the x (horizontal)

and y (vertical) directions. c. Then plug in the numbers and Calculate the net force

in the x direction and then the y direction.d. Extra Credit: Find ax and ay

1. A man pushes a 5kg box with 15 N force to the right while it encounters a 10 N friction force.

2. An 1kg egg is free-falling from a nest in a tree. Neglect air resistance.

3. A 2kg flying squirrel is gliding (no flapping wings) from a tree to the ground constant velocity.

4. A rightward force of 10 N is applied to a 1kg book in order to move it across a desk. Consider a frictional force of 4 N.

5. A 50kg gymnast is suspended motionless from the ceiling by a bar and two vertical ropes, each with a 25 N force.

Problem Solving using FBD’s #F8

1. If a car’s engine accelerates the car using 50,000 N of Force. Friction is resisting the motion with 12,000 N. Find the acceleration of the 2000kg car?

2. If a 60kg skydiver is freefalling towards the ground, and the air resistance half way to the ground is 500 N. What is the net force on the skydiver?

3. From Problem 2, what is the acceleration of the skydiver? 4. If a 70 kg skydiver is freefalling at terminal velocity, what

is the air resistance that the free faller is experiencing. 5. If a 1200 kg car’s engine applies 50,000 N to accelerate

the car and it achieves a 2.5m/s2 acceleration, how much friction is acting on the car? (Assume air resistance is negligible.)

6. If a 20 kg slab of wood is being accelerated on ice at 1.25 m/s2 and friction is small at 5 N. What is the applied force on the slab of wood?