Class 71 Friday, 4/19/24

Warm Up:  What steps do you have to complete before turning in your spreadsheet (and operating your car)?

Class 70 Thursday, 4/18/24

Warm Up: 

None

Class 69.5 Wednesday, 4/17/24

Warm Up: 

1. Why is designing/building your motor so important?  How should you do it?

2.  What if you have to stretch your bands to reach the drive axle?

Class 69 Tuesday, 4/16/24

Warm Up:  After further consideration, I have decided that, on number 7 of the predictions handout, it's okay if the mass flies above the to dotted line -- as long as it doesn't hit the bar.

How does this method determine the energy provided by the rubber bands? 

Class 68.5 Monday, 4/15/24

Warm Up: 

None -- car assembly instructions

Class 68 Friday, 4/12/24

Warm Up: 

The sc

ientist on the right has an insulating disk, a cat fur, and a conducting disk with an insulating handle.  This apparatus can be used to create an electric shock.

1.  What are conductors and insulators?

2.  What are the steps involved in producing the shock?

Class 67.5 Thursday, 4/11/24

Warm Up: 

1.  If you rub a balloon on your head and then hold it next to your hair, your hair is attracted to the balloon.  Why? Triboelectric Series

2.  Your hair may also stand on end after being rubbed by a balloon.  Why?

Class 67 Wednesday, 4/10/24

Warm Up: 

Can you explain how this jar lid mechanism works, in terms of T_net=Frsinθ and  F=kx?

Class 66.5 Tuesday, 4/9/24

Warm Up: 

1. To be stretched a distance X, a single, ordinary rubber band (labeled A in the diagram) requires a force of 1N.  How far must the other configurations (described below) be stretched in order to have that same tension of 1N? [Assume that the rubber bands behave like ideal springs with a constant k.]

B.  2 rubber bands, juxtaposed
C.  2 rubber bands, linked at the end
D. 1 rubber band, cut and arranged into a single strand

2.  If you stretch each of these configurations from rest position to a max force of 1N, which band will store the most energy?

Class 65.5 Friday, 4/5/24

Warm Up: 

1.  A ball is dropped from a height of 3 feet.  At the same time, a bullet leaves a gun barrel traveling horizontally at a height of 3 feet.  Also at the same time, a "frisbee" is thrown horizontally at a height of 3 feet.  Which object hits the ground first?

2.  How do Frisbees^® work?

3. A piece of advice to new ultimate players is to "keep the fast side down."  Which side of the disc is the fast side, and why might this be a helpful thing to do?

Class 65 Thursday, 4/4/24

Warm Up: 

1.  How can you find the North Star?

2.  Why won't this work in 3,000 years?

Class 64.5 Wednesday, 4/3/24

Warm Up:  How does this yo-yo work? What do the springs and steel balls do?

Class 64 Tuesday, 4/2/24

Warm Up:  None

Class 63.5 Monday, 4/1/24

Warm Up:  Suppose you need to want to build a camp fire.  You have plenty of dry wood, but it's all big limbs that are too long to be manageable and too thick to break over your knee.  Without using a saw or an axe, what's the best way to divide the wood into smaller pieces?  Can you describe the proper technique?  One solution.

Class 63 Friday 3/29/24

Warm Up: 

1. If you wanted to calculate the collision force between the container ship and the bridge, what data would you seek?  How would you calculate force?

2. Radians can be problematic in dimensional analysis, because radians is a dimensionless unit.  Explain.

Class 62.5 Thursday 3/28/24

Warm Up: 

Class 62 Wednesday 3/27/24

Warm Up: 

Class 61.5 Tuesday 3/26/24

Warm Up:  The photograph on the right shows a homemade "Gauss Gun."  In the picture there are 9 steel spheres and 4 cube-shaped magnets.  The operator is preparing to roll one sphere toward a magnet.  What will happen, and how will it work?

Today: 

• Return tests
• Check homework
• Review wheel and axle lab -- do a practice problem

Class 61 Monday 3/25/24

Warm Up:  None

Today: 

• Unit 8 (Rotational Motion) Handout  (PDF)
  • Notes: Rotational Kinetic Energy (p. 13, #1,2, and 4) Notes Key
  Video from 2020 -- skip forward to KE
• Momentum Test Retake (optional)

Class 60.5 Thursday 3/21/24

Warm Up: 

A sphere, a cylinder, a thin hoop, and a frictionless box are released from rest at the top of ramp.  Their masses and heights are identical.  There is no air resistance, and everything rolls smoothly, so there is no kinetic friction. 

1.  Rank the objects according to their arrival times at the bottom of the ramp.

2.  Suppose the bottom end of the ramp is frictionless, and when they reach the bottom, the objects hit a vertical, frictionless wall.  What motions, if any, would continue after impact?

3.  How would the results be different if some objects had more mass or greater size than others?

4.  How would the results be different if the ramp itself were frictionless?

Today: 

• Finish the spreadsheet.
• Notes?: Rotational Kinetic Energy (p. 13) Notes Key
Video from 2020 -- skip forward to KE

Class 60 Wednesday 3/20/24

Warm Up:  Given the wheel and axle system on the right, how can we find...

1.  The torque exerted by the string?

2.  The moment of inertia of the wheel and axle?

3.  The torque exerted by kinetic friction?

4.  What assumption are we going to make that is not entirely valid (because it simplifies calculations and isn't super-impactful?

Today: 

• Check/review homework
• Lab:  Finding Moment of Inertia of a Wheel and Axle 
  • Open this spreadsheet and make your own copy. 
  • Set up an apparatus like the one from the warm-up. 
  • Collect the data in the yellow spreadsheet cells.  Follow the "helpful notes."
  • Work your way down the spreadsheet.  For all but the simplest calculations, I suggest deriving a formula on paper first, and entering the formula into the spreadsheet second.
  • Insert formulas into the other cells so that the spreadsheet produces the calculations shown with the example data (see screenshot pasted at the bottom of the sheet).
  • As you proceed, check your success by comparing columns E and F (your formulas vs my formulas).

Class 59.5 Tuesday 3/19/24

Warm Up:  Consider the wheel and axle system on the right.  A string is wrapped around the axle, and a weight is tied to the string.  With the system initially at rest, the weight is released and begins to fall, unwinding the string and turning the wheels and axle. 

What factors determine the rate at which the wheel and axle will rotate?

Today: 

• Check/review homework
• Notes: Dynamics of Rotation (p. 11).   Old Notes Key Video from 2020

Class 59 Monday 3/18/24

Warm Up: 

1.  How can we find the mass of an altered meter stick using only string and a 200g weight?

2.  How can we then find the mass of a bag of clay using only the meter stick and string?

Today: 

• Change: Momentum/impulse retake on Monday, 3/25
• Notes:
  • Angular Acceleration and Intro to Rotational Kinematics (p.7)  Notes key  Video from 2021-22
  • Kinematics of Rotation Notes  (p.9) -- Key (2019 video)

Class 58.5 Friday 3/15/24

Warm Up: 

Today: 

• Return Tests
• Momentum/impulse retake on Monday, 3/25
• Next class -- Notes: Angular Acceleration and Intro to Rotational Kinematics (p.7)  Notes key  Video from 2021-22

Warm Up: 

Today: 

• Test

Homework: 

• None

Class 57.5:

Warm Up: 

Today: 

• Check/review homework.
• Last minute questions about the test?
• Challenge Problem:  Measure the mass of an object using a separate 200g mass, a wooden dowel, and a string, by hanging only one item from the dowel at a time. You may use a meter stick for measuring only, and you may make small marks on the dowel.  You may confirm the mass of the 200g object on a balance, but the balance may not be used for any other purpose.  Your answer must have 5% error or less.

Homework: 

• Test tomorrow

Class 57:

Warm Up: 

1.  What is torque?

2.  Describe how two people of different weights can balance on a seesaw. 

3.  What are the other rotational analogs of the linear quantities we have been working with all year?

Today: 

• Check/review homework.
• Begin Rotational Motion
• Unit 8 (Rotational Motion) Handout  (PDF)
  • Notes:  Torque and balancing torques (p. 1-3)   Torque Notes Key
  • Some practice problems

Warm Up: 

1.  Describe each of the quantities below and explain how each relates to a collision (or any 3rd law pair of forces).

2.  What can a change in one tell us about changes in others?

Today: 

• Check/review homework.
• Test on Tuesday -- here's the format:
  • 3 short answer questions with multiple parts, relating to
    • momentum, impulse, impact force, impact time, coefficient of restitution
    • when momentum is conserved, and when it is not
    • when mechanical energy is conserved, and when it is not
  • 5 problems
    • Ft = change in momentum
    • p = mv
    • conservation of momentum
    • finding velocity with a ballistic pendulum
    • collision with coefficient of restitution, requiring system of equations
• Work time

Homework: 

• 2013-2014 Pennington Quiz (plus an additional coefficient of restitution problem).  Your test will have some short answer questions, and the ballistic pendulum problem will not be a bonus.  Answers/solutions.

Class 55.5:

Warm Up: The pictures on the right show a traditional water wheel followed by two Pelton Wheels.  The Pelton wheels extract more energy from the water.  How?

wikipedia (pelton wheel)  Videos: short --Animation longer --Large Hydroelectric Dam Pelton Wheel

Today: 

• Check/review homework
• As a group, finish your ballistic pendulum calclations, and submit them in Google Classroom.  Check your group's work.

Homework: 

• Answer the questions on page 5 of the handout.  The questions ask "when?"  Limit your responses to "during impact" or "during the swing." Unit 7 Packet (Unit 7 Packet -- PDF Version)

Class 55:

Warm Up: This Top Gear episode features a Renault Modus (compact car) vs. Volvo wagon in a head-on crash. 

1.  What do you expect from this video?

2.  Were you right?

Today: 

• Use a ballistic pendulum to measure the muzzle velocities of various Nerf launchers.  Collect data and complete the spreadsheet.  Ballistic Pendulum Instructions  (PDF)

Homework: 

• Page 13, multiple choice.  Here are the answers...  

Warm Up: None

Today: 

• Optional test retake

Homework: 

• Practice test problem 4 (ballistic pendulum), page 16.  Solution

Class 54:

Warm Up: Assuming that a cart has the same constant acceleration (a) when it is rolling downhill and rolling uphill...

1.  Write an equation for the cart's speed, v_c, attained after being released from rest and accelerating downhill a distance d_c.

2.  Write an equation for the cart's initial speed, v_s, with which it starts rolling uphill before accelerating to a stop after a distance d_s.

3.  Write an equation for the coefficient of restitution (e) for the collision that occurs after the cart accelerates a distance d_c toward the collision point and just before it rebounds a distance d_s away from the collision point.  Assume that the car starts and ends at rest and that its acceleration is always directed toward the collision point.

Today: 

• Check/review homework

• Solve a ballistic pendulum problem (p. 6 and 5) -- calculations first, theory second.

• Get in groups, finish the lab questions.  Then complete the short group quiz.

• Compare lab answers.  Discuss.

Warm Up: 

None

Today: 

• Mr. Stapleton is at the courthouse.
• Work on the homework.

Homework: 

• Practice test on p. 14-16, except for problem #4 (ballistic pendulum).
  • Short Answer: some possible answers
  • Problems: Solutions

Class 53:

Warm Up: 

Suppose you start up the Newton's cradle by pulling aside and then releasing one sphere.  As the cradle does its thing...

1. When is the collective momentum of the all of the spheres conserved?  How can you tell?

2.  When is the collective momentum of the spheres not conserved?  How can you tell? Why?

3.  What happens to the total mechanical energy of the spheres as they move back and forth?

4.  What happens to their total kinetic energy?

5.  What other type(s) of mechanical energy do the spheres have during their movements?

6.  What happens when you pull aside and then release two spheres?  Three?  Four?  Why?

7.  Would it be possible to build a Newton's cradle that "kicks out" a number of spheres that is different from the number that cause the collision?  If so, how?

Today: 

• A5/6 follow-up to yesterday's warm-up.  And did anyone calculate e for the collision that I described?
• A7/8 check/review homework
• I have a jury summons tomorrow, so you'll have a susbstitute.  Spend tomorrow's class working on the homework or preparing for the work/energy test retake.
• The test retake will be on Friday.  If you think you'll need more than a split block, try to arrange spending both split blocks in physics.
• Lab -- collisions with a force meter.  Finish and discuss the answers.
• Work time

Homework: 

• Due on Thursday:
• Practice test on p. 14-16, except for problem #4 (ballistic pendulum).
  • Short Answer: some possible answers
  • Problems: Solutions

Class 52.5:

Warm Up:  Suppose I place some foam on my table top, and then I shoot it with the two darts in the picture, using the same Nerf ^® gun.  Compare the effects of the two darts impact on the motion of the foam.

Today:Today: 

• Return the tests -- after some people finish.  Distribution...
• 5/6 -- check/review the homework.
• A7/8 Only -- Notes:  Elastic and Inelastic collisions + Coefficient of Restitution -- p. 3-4.
  • Notes key
  • Videos from 21-22 year:
    • Momentum and Impulse Notes Video -- pages 1-2
    • Conservation of momentum notes video -- page 3
• If there's time in A5/6 -- start figuring out how to find closing speed once you collect lab data.

Homework: 

• A5/6 -- no homework
• A7/8 Only -- Problems 13-14 on packet p. 9. 
  • Problem solutions

Warm Up:  None

Today: 

• Test

Homework: 

• A5/6 Only (A7/8 will do this later) -- Due on Monday -- Problems 13-14 on packet p. 9.  Answers are at the bottom of page 10.
• Problem solutions

Class 51.5:

Warm Up: 

Today: 

• Check/review homework
• Unit 7 Packet (Unit 7 Packet -- PDF Version)
• A5/6 Only -- Notes:  Elastic and Inelastic collisions + Coefficient of Restitution -- p. 3-4.
  • Notes key
  • Videos from 21-22 year:
    • Momentum and Impulse Notes Video -- pages 1-2
    • Conservation of momentum notes video -- page 3
• Questions about tomorrow's test?

Homework: 

• A5/6 Only (A7/8 will do this later) -- Due on Monday -- Problems 13-14 on packet p. 9.  Answers are at the bottom of page 10.
• Problem solutions
• Prepare for the test.

Class 51:

Warm Up: 

Today: 

• Check/review homework
• Unit 7 Packet (Unit 7 Packet -- PDF Version)
• Notes:  Momentum, Impulse, and Conservation of Momentum -- get through #17 on p. 3.
  • Notes key
  • Videos from 21-22 year:
    • Momentum and Impulse Notes Video -- pages 1-2
    • Conservation of momentum notes video -- page 3

Homework: 

• Optional test retake on Wednesday.
• Problems 4-9 on packet p. 7-8.  Answers are at the bottom of page 10.

  • Problem solutions updated

  • Video explaining problems 1-6

  • Homework help video for problems 7-10

Class 50.5:

Warm Up: 

Today: 

• Unit 7 Packet (Unit 7 Packet -- PDF Version)
• Notes:  Momentum, Impulse, and Conservation of Momentum
  • Notes key
  • Videos from 21-22:
    • Momentum and Impulse Notes Video -- pages 1-2
    • Conservation of momentum notes video -- page 3

Homework: 

• Problems 1-3 on packet p. 7-8.  Answers are at the bottom of page 10.

  • Problem solutions updated

  • Video explaining problems 1-6

  • Homework help video for problems 7-10

Class 50:

Warm Up: 

Today:

• More test review
  • The big picture -- what happens to energy
  • The list of tools
  • Practice:
    • Energy video situations revisited.   Here's the handout -- PDF.  For each scenario, I wrote an equation  and a verbal description.  You should be able to do the same.  You should also be able to generate an equation based on the description, and vice-versa.  I did not double-check my answers; please let me know if you discover mistakes.
      • Write the simplest possible equations representing what is happening in each numbered situation.  Here are my equations.  The thing that makes them the simplest is that quantities that change are assumed to be zero on one side of the equation.
      • Write verbal descriptions for each of these scenarios.  I kept mine generic (e.g. "a mass m is lowered a height h while a spring with constant k is compressed a distance x.).  These could form the basis for test problems -- all you would have to do is replace the variables with numbers (except for the varible that the solver of the problem is trying to find).  Here are my verbal descriptions.  They are not necessarily the only acceptable descriptions.
    • Extra Test Review questions and problems. (PDF)  Solutions -- let me know if you think you see mistakes.  If you can do all of these, correctly, on your own, without looking anything up, you are probably all set to take the test.  If you can't do them on your own, you still may be okay on the test.  They're a little harder than the test.

Homework:

• Test on Friday.  We will start the momentum unit tomorrow.