DAY 27

#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

Warm-Up (4min)

Copy and fill in (or choose) the correct answers for the following:

• 1. What is the equation which represents Newton's 2nd Law of Motion?
• 2. What mathematical operation does Σ represent?
• 3. What are the units of a Newton?
• 4. Draw a free body diagram representing a book, sliding on a horizontal table, with applied force of +10.0N, and friction of -4.5N.

CLASSWORK

1. #026C (continued): Modeling and Practice

• We're going to continue to help each other. From yesterday, here's our list of best tutoring practices:
  • Don't give student the answer
  • let student think on their own
  • ask guiding questions
  • guide student to figure out mistakes
  • be nice, calm, patient, supportive
  • try to make student solve problem
  • review the topic (this is a great way to guide students thru finding their mistake)
  • give a person a fish vs. teach a person to fish

Practice Problems

1. A book is at rest on a tabletop. Diagram the forces acting on the book.
2. A gymnast holding onto a bar, is suspended motionless in mid-air. The bar is supported by two ropes that attach to the ceiling. Diagram the forces acting on the combination of gymnast and bar.
4. An egg is free-falling from a nest in a tree. Neglect air resistance. Diagram the forces acting on the egg as it is falling.
6. A flying squirrel is gliding straight down (no flapping of the wings) from a tree to the ground at constant velocity. Consider air resistance. Diagram the forces acting on the squirrel.
8. A rightward force is applied to a book in order to move it across a desk with a rightward acceleration. Consider frictional forces. Neglect air resistance. Diagram the forces acting on the book.
10. A rightward force is applied to a book in order to move it across a desk at constant velocity. Consider frictional forces. Neglect air resistance. Diagram the forces acting on the book.
12. A college student rests a backpack upon his shoulder. The pack is suspended motionless by one strap from one shoulder. Diagram the vertical forces acting on the backpack.
14. A skydiver is descending with a constant velocity. Consider air resistance. Diagram the forces acting upon the skydiver.
16. <Happy Valentines Day - complete the three problems below>
17. A force is applied to the right to drag a sled across loosely packed snow with a rightward acceleration. Neglect air resistance. Diagram the forces acting upon the sled.
19. A football is moving upwards towards its peak after having been booted by the punter. Neglect air resistance. Diagram the forces acting upon the football as it rises upward towards its peak.
21. A car is coasting to the right and slowing down. Neglect air resistance. Diagram the forces acting upon the car

#027A: Determining the Net Force

Notes:

• An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
• If either all the vertical forces (up and down) do not cancel each other and/or all horizontal forces do not cancel each other, then an unbalanced force exists.
• Review the following. Are the forces balanced?

• If the forces are unbalanced, a NET FORCE exists
• What is the net force in each of the above?
• So what? Well, a net force causes acceleration, and we can use that fact to solve problems.

#027B: A Net Force Causes Acceleration - Practice Problems

• Navigate to: http://www.physicsclassroom.com/class/newtlaws/Lesson-2/Determining-the-Net-Force
• Scroll halfway down the page to "A Net Force Causes Acceleration "
• Looking at the Descriptions of Motion, what is the net force for each scenario? (answers can be positive, negative, or zero)
• Try the two Check for Understanding problems on your own for practice. Get peer help if needed.

At Home Learning (HW)

1. Complete Lab #2 due Thursday

This should include the following. Topics in CAPS are especially important.

Names & Group Member Names

Purpose

Materials

PROCEDURE

this should be specific/detailed enough that another person could read them, and do the lab correctly.

DATA

time data from finding Δx

SAMPLE CALCULATIONS

show how you did all the math leading up to, and including, solving Δx=v_ixΔt

RESULTS

what happened?

ANALYSIS

- Any errors? If so, which ones, and how did they affect your results?

- If you didn't have any errors, why not? What steps did you take that made your lab work so well?

Conclusion

- Sum up the lab, the experience, how did it go?

If you'd like to use the template and see the rubric, here they are again

Grading Rubric LINK

Lab Template: LINK

2. #027C: Your homework, due Thursday, is to prepare for class by watching 8.5 minutes worth of video. You should understand how to solve net force problems after watching the video

Take Notes: Introductory Newton's 2nd Law Example Problem

Watch the video, and answer the EdPuzzle Questions: EDpuzzle

NGSS Standard

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.]