Goals: SWBAT...
1. Draw correct Fg and FN vectors.
2. Say when forces are balanced and when they aren't balanced.
3. Draw correct FBD's, with appropriate vector magnitude and direction.
4. Support classmates with helpful tutoring
Warm-Up (4min)
Copy and fill in (or choose) the correct answers for the following:
1. FBD stands for _____ ______ ______
2. The size of the vector arrow in a FBD represents the _________ of the force.
3. In which direction does the force of gravity ALWAYS work?
4. If forces are unbalanced, the velocity will be (constant/accelerating).
5. Draw both FBD's. Which FBD on the board is correct? Why is the other one incorrect? (Hint: There's only one thing wrong)
CLASSWORK
1. 042A: Classwork Review (3min)
2. 042B: Homework Questions? (3min)
3. 042C: NOTES: Review of How-To Draw Free Body Diagrams (FBD's) (5min)
Notes:FBD's show magnitude and direction of all forces acting upon an object.
Vector size represents the magnitude of the force.
Vector direction shows the direction the force is acting.
Each vector needs a label
The object is represented by a box and the force vector is drawn from the center of the box outward in the direction that the force is acting. An example of a free-body diagram is shown at the right.
Fg is always down
FN is always perpendicular (90*) to the surface. Often that means up, but not always... (object on an incline)
4. 042D: NOTES: Process for Drawing a FBD (3min) (edit this for next year; find a & v directions, list forces, balanced/unbalanced?, which force 'wins'?, draw box/forces, label vectors)
When given a description of a physical situation, identify which forces are present.
Determine the direction in which each force is acting.
Draw a box and add vectors for each existing force in the appropriate direction
Label each force vector according to its type
5. 042E: Modeling and Practice (24 min)
- 12 situations
- for each, in your notes:
- describe the situation using terms like velocity, acceleration, up/down, left/right
- draw the FBD
Learning at Home (HW)
1. #042F: Your homework, due Wednesday, is to prepare for class by watching 9.5 minutes worth of video. You should understand how to solve net force problems after watching the video. You should also know what this symbol ∑ means...
Watch the video, and answer the EdPuzzle Questions: EDpuzzle
GOALS: SWBAT...
1. state how changes in net force and mass affect acceleration
WARM-UP
Defining Newton's First Law (2min)
Complete the following, and think about the water in the plate:
An object at rest stays at ____ and an object in motion stays in _____ with the same speed and in the same direction unless acted upon by a net _________ force.
CLASSWORK
042A: Applying Newton's 1st Law of Inertia (30min)
Today you'll explore the realtionship between mass and acceleration
Handout (copy chart): https://www.physicsclassroom.com/Physics-Interactives/Newtons-Laws/Force/Force-Exercise-1
Interactive LINK: https://www.physicsclassroom.com/Physics-Interactives/Newtons-Laws/Force/Force-Interactive
Learning at Home (HW) (3 min)
1. Free Body Diagrams - What are they?
- Video Edpuzzle LINK
- Sample Notes LINK
2. #041F: Lab Conclusion & other lab info
Complete Ball in a Cup Lab, due Wednesday @ 11:59pm, submitted electronically via the pre-lab document (which you already shared with me). Note, there is no hypothesis this time
This should include the following.
TITLE Ball in a Cup Lab
NAMES & GROUP MEMBERS NAMES
PURPOSE
set of instructions
MATERIALS
list them
PROCEDURE
this should be a list of instructions specific/detailed enough that another person could read them, and do the lab correctly.
DATA
small chart of time data for finding Vx
free-fall time calculation for finding Δt
calculation showing how you found Δx for the cup
***note that you can take a photo of your neat math work showing the above
SAMPLE CALCULATIONS should be included in the DATA section, or immediately following the DATA section
show how you did all the math leading up to, and including, solving Δx=vixΔt
RESULTS
what happened? (where did the ball land? Using your video, you can take a screenshot of the ball landing in the cup (or missing) and upload it to your document).
ANALYSIS
- Any errors? You'll need to be specific when discussing errors. For example:
- state where in an equation you made a mistake, and how that mistake affected your results
- describe a physical error (mistiming the displacement zone for vx, releasing the ball from too high/too low, tilted table, wrong angle for ramp, etc), and state how it/they affected 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 - describe if you were/weren't successful. What might you do differently next time to be more successful?
If you'd like to use the template and see the rubric, here they are again
Grading Rubric LINK
Lab Template: LINK
Note to self: next year do a better job of separating conservation and non-conservation. There was too much bleeding over this year - and a few occasions of back and forth.
#Goals: SWBAT...
1. Categorize forces as internal or external
2. Understand how internal vs. external forces affect the TME
2. Answer basic energy conservation questions
QUIZ FIRST :-) Then complete the warm-up & #042A
Warm-Up (4min): Internal vs. External Forces
Categorize the following as either internal or external forces.
Fa, Ff, Fair, Ftension, FN, Fg, Fspring
Read, then complete the fill-in activity. For your warm up, you can just write the "fill in the blank" words.
If two parts of a system exert forces on each other, those forces are said to be internal forces for the system.
An external force is a force between a part of a system and something outside the system.
So whether a force is internal or external depends on what you define as your system.
Examples:
1) A baseball. The forces holding the particles of the baseball together are internal forces; the force of a bat hitting the ball is an _________ force on the ball; so is gravity.
2) A cat and dog fighting in a sack. The two are killing each other, but considered as one system the forces they exert on each other are all internal.
3) The cat and dog considered separately. Considering the cat as a separate system, forces between the cat and the dog are now ________ forces.
4) A car. The parts of the car exert forces on each other: the pistons push the rods, the axle pushes the wheels, etc. All these forces are _______ to the car as a whole. But the friction that the ground exerts on the tires is an ________ force. So is the weight of the car, and the force the ground exerts to hold up the car.
CLASSWORK
1. #042A: So, What Does Work Do??? Notes
If I apply a force to an object, do I change the amount of energy it possesses? In other words, if I push something, do I change it's energy? Think about it.
What if I do work on an object? Does that change it's energy?
Talk it over with your neighbor, then prepare to share.
TAKE NOTES ON THE FOLLOWING
NON-CONSERVATIVE FORCES:
When net work is done upon an object by an external force, the total mechanical energy (KE + PE) of
that object is changed. If the work is positive work, then the object will gain energy.
If the work is negative work, then the object will lose energy.
The gain or loss in energy can be in the form of potential energy, kinetic energy, or both.
Under such circumstances, the work that is done will be equal to the change in mechanical energy of the object.
Because external forces are capable of changing the total mechanical energy of an object, they are sometimes referred to as nonconservative forces.
CONSERVATIVE FORCES:
When the only type of force doing net work upon an object is an internal force (for example, gravitational and spring forces), the total mechanical energy (KE + PE) of that object remains constant.
In such cases, the object's energy changes form.
For example, as an object is "forced" from a high elevation to a lower elevation by gravity, some of the potential energy of that object is transformed into kinetic energy. Yet, the sum of the kinetic and potential energies remains constant. This is referred to as energy conservation.
When the only forces doing work are internal forces, energy changes forms - from kinetic to potential (or vice versa); yet the total amount of mechanical is conserved.
Because internal forces are capable of changing the form of energy without changing the total amount of mechanical energy (TME), they are sometimes referred to as conservative forces.
2. 042B: How do Internal Forces Affect KE and PE?
When the only forces doing work upon the objects are internal forces - gravitational and spring forces - TME stays the same. Thus, energy is transformed from KE to PE (or vice versa) while the total amount of mechanical energy is conserved. Read each description for the practice, and indicate whether energy is transformed from KE to PE or from PE to KE.
Questions are here: LINK
First question looks like this:
A ball falls from a height of 2 meters in the absence of air resistance.
3. #042C: Positive vs. Negative Work and Energy Change
answer the six scenario questions
At Home Learning (HW)
1. Friday we'll be solving some pretty complex TME problems. Prepare by looking at all three examples here: LINK
2. #042C: TME Practice with Flipping Physics: Watch/take notes/complete edpuzzle questions on the following:
(8:58) Introductory Work due to Friction equals Change in Mechanical Energy Problem - EDpuzzle
3. EXTRA CREDIT: For credit, you'll need to show all work. Due by friday.
A. A wagon is pulled by a force of 38.0 N exerted on the handle at an angle of 42.0° with the horizontal. If the wagon is pulled in a circle of radius 20.0 m, how much work is done?
B. A 120-kg lawn tractor, shown in Figure 10-17 (pg 279 --> LINK), goes up a 21° incline that is 12.0 m long in 2.5 s. Calculate the power that is developed by the tractor.