DAY 75
#Goals: SWBAT...
1. ... list and describe the basic components of "Work"
2. ... solve basic work problems
WARM-UP:
1. In the video, when Billy was holding the dictionary, was he doing work? Why or why not?
2. Draw a stick figure of a person holding a book, similar to the picture next to the projector screen
3. As I lift a book upward, draw a vector arrow from the book in the direction of the force I'm applying. Also, draw an arrow next to the book showing the direction of the displacement of the book. What is the angle between the two arrows? What is the cosine of that angle?
4. Find the sign of the work by using the equation W=Fdcos(ϑ)
5. As I lower the book downward, draw a vector arrow from the book in the direction of the force I'm applying. Also, draw an arrow next to the book showing the direction of the displacement of the book. What is the angle between the two arrows? What is the cosine of that angle?
6. Find the sign of the work by using the equation W=Fdcos(ϑ)
CLASSWORK:
1. Add Work to your Equation Chart/Table of Friends
Symbol: W
Equation: W=Fdcos(ϑ)
Definition: the change in the amount of kinetic energy of a system
What does kinetic mean? --> movement
Vector or Scalar? Scalar
2. Intro to Work Quiz
3. What is Work?
https://ed.ted.com/on/5bau54uF
Answer the 9 thinking questions in your notes
4. How do we find the work on a shopping cart?
A. Brainstorm:
- What information would you need to solve the problem?
- Which equation(s) would you use?
- What are the forces on the cart? (draw an FBD)
B. Solve the problem http://www.flippingphysics.com/work-problem.html. Copy the solutions into your notes.
A nice write-up of the solution is here: http://www.flippingphysics.com/uploads/2/1/1/0/21103672/0137_lecture_notes_-_introductory_work_problem.pdf
HOMEWORK
A. Complete problems 1-9 from the TedEd
B. Look at Example problem #1 pg 261. Solve pg 261 1-2
#Goals: SWBAT...
1. ... solve an advanced work problem
2. ... review concepts of KE and PE
3. ... collect data for Conservation of Energy Lab
WARM-UP:
John pushes a crate across the floor of a factory with a horizontal force. The roughness of the floor changes, and John must exert a force of 20 N for 5 m, then 35 N for 12 m, and then 10 N for 8 m.
a. Draw a graph of force as a function of distance.
b. Find the work John does pushing the crate.
CLASSWORK:
1. Lab
HOMEWORK:
In case you didn't already do it, do it now :)
1. Watch: http://www.flippingphysics.com/intro-ke.html
2. Is KE a vector or scalar? Can it be negative?
3. As you watch the video, take note and copy the solution for the example problem.
4. Why do we only need the speed (and not the velocity) of the bike or car to solve the problem?
5. What mistake was (almost) made at around 3:30 of the video?
6. Solve a similar problem: Pedro is skateboarding at 4m/s. He has a mass of 55kg, and his skateboard has a mass of 3.0kg. His buddy Napoleon has a mass of 85kg. How fast must Napoleon run to have the same KE as Pedro?
Alexander's notes to self:
http://physics.mercer.edu/labs/manuals/manualMECHlab/energyConservation/energyConservation.pdf
http://www.udel.edu/GK-12/Material/2007/CM/Ekiert/Labs/Conservation%20of%20Energy%20Lab.pdf
http://mrsj.exofire.net/ipc/docs/energycons_lab.pdf
https://docs.google.com/document/d/15vogKUCJ4um7l4otcz7Akm_7-6vMkXytu-xR16MZNiU/edit