DAY 48

NGSS Standard (this is what we're learning with this unit)

Analyze data to support the claim that Newton’s second law of motion describes the mathematical relationship amongthe net force on a macroscopic object, its mass, and its acceleration. [Clarification Statement: Examples of data could include tables or graphs of position or velocity as a function of time for objects subject to a net unbalanced force, such as a falling object, an object sliding down a ramp, or a moving object being pulled by a constant force.] [Assessment Boundary: Assessment is limited to one-dimensional motion and to macroscopic objects moving at non-relativistic speeds.]

#GOALS: SWBAT....

1. Use FBD's to find Net Force, mass, acceleration

2. Use mu and Fn to find Ff.

3. Explain the relationship between mass, Fn, and the behavior of a horizontally moving object

WARM-UP

A rightward force is applied to a 10-kg object to move it across a rough surface at constant velocity. The coefficient of friction between the object and the surface is 0.2. Use the diagram to determine the gravitational force, normal force, applied force, frictional force, and net force. (Neglect air resistance.) (hint: find Fg first, then Fn. Calculate Ff, then find Fa)

CLASSWORK

1. 048A: Rocket Sled (friction sim)

    - handout/instructions: Read, then complete: LINK

        In case "Complete" isn't enough instructions for you, here's more details ;-).

        1. look at the .pdf Read the instructions at the top

        2. Draw the FBD's for #1 and #2, then answer question #3    

        3. Draw the FBD for #4, then answer #5, 6, and 7

        4. Draw the five FBD's for the assessment, summarize the five answers choices, and match the FBD's to the answers.

    - simulation activity: LINK

LEARNING AT HOME (HW)

- No new learning at home assignments tonight, however if you don't finish the classwork today, you'll need to finish it tonight.

- Make sure you know how to solve free body diagram problems like the one in the warm up today. There will be a quiz on these Friday or Monday.

NGSS Standard (this is what we're learning with this unit)

Analyze data to support the claim that Newton’s second law of motion describes the mathematical relationship amongthe net force on a macroscopic object, its mass, and its acceleration. [Clarification Statement: Examples of data could include tables or graphs of position or velocity as a function of time for objects subject to a net unbalanced force, such as a falling object, an object sliding down a ramp, or a moving object being pulled by a constant force.] [Assessment Boundary: Assessment is limited to one-dimensional motion and to macroscopic objects moving at non-relativistic speeds.]

#Goals: SWBAT...

1. Draw correct FBD's, with appropriate vector magnitude and direction.

2. Support classmates with helpful tutoring

3. Use FBD's to find Net Force

4. Describe the relationship between mass, net force, and acceleration

WARM-UP (review of your Friction HW notes) (8min)

1. What is the symbol for the force of friction?

2. Define "Static"

3. Define "Kinetic"

4. Does the amount of friction depend on surface area? (AKA, would a truck with four tires feel different friction from a truck with six tires?)

5. Does friction oppose the direction of motion?

6. Does friction oppose the direction of the force applied?

7. Is friction perpendicular to the sliding surface, or parallel to it?

8. What does a smooth surface look like under a microscope? Still smooth, or rough?

9. Which is more difficult: Getting an object moving, or keeping it moving?

10. What is the symbol for the coefficient of friction (mu) and what are it's units?

CLASSWORK

1. HW Review

2. #048A: Finding Acceleration, Fnet, or mass via FBD's

The net force is the vector sum of all the individual forces. 

In this lesson, we will learn how to determine the acceleration of an object if the magnitudes of all the individual forces are known. 

The three major equations that will be useful are 

the equation for net force (Fnet = m•a), 

the equation for gravitational force (Fg = m•g), 

and the equation for frictional force (Ff = μ • FN).   <------THIS IS NEW! :-)  A really cool thing about the equation for friction is it's dependence on the normal force. Think about what happens when you try to go up a steep hill. 

    - In what direction does the gravitational force pull you?

    - In what direction does the normal force push you?

    - As a hill gets steeper, what happens to the direction of the normal force? 

The process of determining the acceleration of an object demands that the mass and the net force are known. If mass (m) and net force (Fnet) are known, then the acceleration is determined by use of the equation.

a = Fnet / m

Your Turn to Practice

Thus, the task involves using the above equations, the given information, and your understanding of Newton's laws to determine the acceleration. To gain a feel for how this method is applied, try the following practice problems. ALWAYS START BY SUMMING THE FORCES IN THE X and Y.

Practice #1

An applied force of 50 N is used to accelerate an object to the right across a frictional surface. The object encounters 10 N of friction. Use the diagram to determine the normal force, the net force, the mass, and the acceleration of the object. (Neglect air resistance.)

A rightward force is applied to a 6-kg object to move it across a rough surface at constant velocity. The object encounters 15 N of frictional force. Use the diagram to determine the gravitational force, normal force, net force, and applied force. (Neglect air resistance.)

Practice #2

At Home Learning (HW) 

1. #048C: Your homework, due Thursday, is to prepare for class by watching 10 minutes worth of video. You should understand how to solve net force and friction problems after watching the video, and doing the three practice problems. Pause the video after the teacher describes the scenario, try the problem on your own, then un-pause the video, and check to see if your solution was correct. Be sure to write the problem and solution into your notes. 

The video is here --> LINK

#Goals: SWBAT...

1. Use scientific reasoning to answer impulse and momentum questions

2. Understand that a shorter time period (smaller delta t) results in a (larger/smaller) force

3. Use the impulse-momentum equation to solve momentum/impulse problems. 

Warm-Up (5min):

HW check: chart, edpuzzle/notes. Warm-ups 39-48 later today during class

Recall: Impulse = F • t       &      Change in Momentum = m • ∆v     

            Impulse = Change in Momentum   so....    F • t = m • ∆v

CLASSWORK

1. #048A: Relating Impulse and Momentum via a Virtual Egg Drop

At Home Learning (HW) 

1. if necessary, complete 048A

2. #048B: Take notes/answer edpuzzle questions here (2 videos):

(9:57) How to Wear a Helmet: a PSA from Flipping Physics - EDpuzzle

(3:58) Introduction to Conservation of Momentum with Demonstrations - EDpuzzle

    

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2. #048B: 

We will solve example problem #1-1 together, and you'll do #1-2 and #2