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00. Unit 2 Force Notes

1 discussed new material for Unit 2H - Forces:

• discussed video demo and developed Newton's 1st Law: An object will maintain a constant velocity unless acted upon by a net force

2. reviewed how pushes/pulls (forces) change motion (data here)...students came up with Newton's 1st Law: An object will maintain a constant velocity unless acted upon by a net force (defined as a push or pull in a particular direction) (summary here)

3. Discussed types of forces...developed the idea that the normal force is the force that a surface exerts on an object touching it...it is called the "normal force" since it pushes out always in a perpendicular, or normal, direction (force catalog here)

4. Discussed the nature of the normal force - normal forces are forces that occur when surfaces push against each other. The direction of this force is always perpendicular (or normal) to the surface.

5. discussed interaction diagrams (also called system schema) - a diagrammatic method for determining the force interactions in a system ... schema notes here

6. students worked on Unit 2 Practice 1 , a series of situations in which students identified the forces acting on a block and sketched appropriate force diagrams...each vector representing a force was labeled using the "on,by" subscript notation.

7. discussed some of the force diagrams associated with Unit 2 Practice 1

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00. Unit 2 Force Notes

1. discussed remaining force diagrams associated with Unit 2 Practice 1

2. performed the following experiment as a demonstration experiment: tggamm the relationship between the gravitational force, Fg and mass, m ... the result was Fg=(9.8)m where 9.8 had units of N/kg

3. students observed that 9.8 m/s^2 and 9.8 N/kg must be the same quantity...this allows us to define the N,

4. 1N=(kg)(m)/(s^2)

5. discussed the nature of the friction force: there is a static friction force and a kinetic friction force ... the friction force, Ff, depends on the coefficient of friction, mu, and the normal force, N in the following fashion: Ff=(mu)(N) via a friction experiment

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1. Unit 2 Force Notes

2. continued discussing the nature of the friction force: there is a static friction force and a kinetic friction force ... the friction force, Ff, depends on the coefficient of friction, mu, and the normal force, N in the following fashion: Ff=(mu)(N) via a friction experiment

3. developed Newton's 3rd Law : Fa,b = - Fb,a .... showed a video demonstrating this law: go here

4. began solving simple problems involving the use of force diagrams

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1. Unit 2 Force Notes

2. continued solving simple problems involving the use of force diagrams

3. ran into a problem that involved an off-axis force ... discussed the process for replacing off-axis forces with components

4. discussed the PacMan Rule

5. discussed a physical situation in which a block is stationary on an incline...found mu given the angle of the ramp and the mass of the block

6. discussed more examples with Fnet=0 but with one or more forces off axis ... used PacMan Rule to quickly replace off axis forces with components in order to write and solve equations

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1. Unit 2 Force Notes

2. discussed more examples with Fnet=0 but with one or more forces off axis ... used PacMan Rule to quickly replace off axis forces with components in order to write and solve equations

3. discussed a physical situation in which a block is stationary on an incline...found mu given the angle of the ramp and the mass of the block

4. students conducted the Pivot Interactives lab titled: Fan Cart: Force & Acceleration (Scaffolded)

5. students will conduct the Pivot Interactives lab over the weekend titled: Fan Cart: Mass & Acceleration (Scaffolded)

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1. Unit 2 Force Notes

2. discussed the Pivot Interactives lab titled: Fan Cart: Force & Acceleration (Scaffolded)

3. I conducted the Pivot Interactives lab titled: Fan Cart: Mass & Acceleration (Scaffolded) over the weekend and discussed the results

4. Reviewed forces so far:

• force is a push/pull

• N1L

• w=mg

• f=(mu)N

• N3L

• PacMan Rule for dealing with off-axis forces

• N2L

5. began discussing dynamics (Fnet =ma) problems

6. discussed how dynamics problems are related to 1D motion problems: Find Fnet, use Fnet=ma to find a, given certain motion quantities along with a, figure out other motion quantities.

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1. Unit 2 Force Notes

2. discussed a very involved problem requiring the use of the interaction diagram (for CV and then for CA motion)

3. continued discussing dynamics (Fnet =ma) problems

4. reviewed two con-CA motion problems and connected a(t) to F(t)

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1. Unit 2 Force Notes

2. continued discussing dynamics (Fnet =ma) problems

3. discussed a traditional Atwood's Machine problem

4. discussed a modified Atwood's Machine

5. discussed an example in which motion information was given so one can find info about a, then use a and Fnet=ma to find Fnet, then use Fnet to determine info about individual forces

6. given components, find actual force magnitude and direction

7. discussed free fall (no air)

8. viewed several video clips of objects falling in no air: bowling ball vs. feathers , hammer and feather on moon

9. began discussing free fall (with air assuming R=bv)

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1. Unit 2 Force Notes

2. derived v(t) and a(t) for ball falling through air feeling a resistance force R=bv ... notes here

3. discussed the conceptual setups for problems from the following packet containing these document : hwA

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1. Unit 2 Force Notes

2. coffee filter over motion detector to demonstrate change of motion from acceleration to terminal (CV) velocity due to air resistance ... Pivot Interactives Lab: Falling Coffee Filters must be completed by Monday's class.

3. discussed the conceptual setups for problems from the following packet containing these document : hwB , and hwC

4. handed out M1-M4 ... students must do M1 and M2 by Monday

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1. Unit 2 Force Notes

2. discussed results of Pivot Interactives Lab: Falling Coffee Filters

3. continued discussing M1-M4 (talked about solutions for M1 and M2)

4. discussed progressively more difficult problems

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1. Unit 2 Force Notes

2. discussed progressively more difficult problems

3. students worked M3 and M4 in class

4. students worked on Mastering Physics assignment due tomorrow night

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1. Unit 2 Force Notes

2. students need to finish MasteringPhysics assignment by 11:59pm today.

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1. Unit 2 Force Notes

2. Mechanics Exam MC go over. FR go over.

3. discussed remaining problems from the notes

4. students did the first two MC assessments from AP Classroom

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1. Unit 2 Force Notes

2. Mechanics Exam MC go over. FR go over.

3. we discussed the solutions to the three free response questions from this review packet (Chapter 1)...students worked free response questions from unit 2.

4. students did the third MC assessment from AP Classroom

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1. Unit 2 Force Notes

2. Mechanics Exam 2

3. began Unit 3 material

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