Due 11/3: HW: Circular Motion I

1. Distinguish between rotation and revolution. Draw an example of each and label them!
2. If you lose your grip on a rapidly spinning merry-go-round and fall off, in which direction will you fly? Draw a diagram of the overhead view to help you answer.
3. A ladybug sits halfway between the axis and the edge of a rotating turntable. Drawing a diagram may help! What will happen to the ladybug's tangential velocity if:
a. The rotational speed is doubled?
b. The ladybug sits at the edge?
c. Both a and b occur?

Friday, 10/31: Intro to Circular Motion

Topics: rotation, revolution, linear (tangential) speed, and rotational (angular) speed. Notes on left.

Thursday, 10/30: Special Assignments

This is the last day to finish the special assignments we started on Tuesday. See Tuesday's post for the details.

Also today: notebook checks and teacher stamp counts.

Wednesday, 10/29: Special Assignments

We're still working on the special assignments we started yesterday. See yesterday's post for details.

Tuesday, 10/28: Special Assignments

Over the next three days you will be given time to complete these 2 assignments:

1.) Vocabulary Cards OR Riddle Cards. Instructions are in your notebooks. Choose one of these assignments for the following vocabulary words:

work
kinetic energy
potential energy
conservation/conserved
momentum
impulse

If you do both, I will give extra credit for the second one.

2) Your choice of these three assignments for any physics topic we have covered this year:

Tatoo or Body Art
Tee Shirt Art
Designing a Magazine Ad

Again, the instructions for each are in your notebook. PLEASE complete all parts of whatever assignment you choose!

In the last 20 minutes of Thursday your group will grade your two assignments and we will also do notebook checks. So have your assignments ready on Thursday!

Monday, 10/27: Energy practice

Today we worked through the problem of a roller coaster car that started from rest at the top of a 7.2 meter high hill. We found the total energy, the kinetic and potential energies at three different points, and the point at which the speed of the car is greatest. We then used this problem to go over several similar problems on Concept-Developments 8-1 and 8-2.

Over the next three days, quite a few students will be pulled from class to take AIMS. I don't want these students to miss our introduction to rotational motion, so instead we're going to work on some of those special assignments we taped into our notebooks at the beginning of the year. We'll use topics from the last few weeks.

Friday, 10/24: Teacher is out!

I'm out at some training for MESA, so today you have two worksheets to complete: Concept-Development 8-1 and 8-2. These are about energy, work, and mechanical advantage and are due on Monday. These are not easy! Do not leave them to the last minute!

Have a great Homecoming!

Thursday, 10/23: Kinetic and Potential Energy

We started with a bellwork problem and then everyone worked on a self-tutorial about energy. This can be found at: http://docs.google.com/Doc?id=dccgmhcd_21f52m3kfs. Ignore the funny numbering; I'm still trying to get comfortable with Google Docs.

After that we talked a bit more about energy, the law of conservation of energy, and work. If you want notes, you'll have to talk to your classmates; the class notebook is still missing.

No homework tonight.

Wednesday, 10/22: Machines and Mechanical Advantage

Today we used our results of the pulley lab to discuss machines and mechanical advantage. Unfortunatey, someone has walked off with the class notebook, so until it is returned there will be no notes available.

Tuesday, 10/21: Pulley Lab Continued

We finished making pulley systems today. Please finish all the math tonight and have it ready for tomorrow.

Monday, 10/20: Pulley Lab

Today we started an exploratory lab involving pulleys. We will be finishing it tomorrow. Basically, your task is to build as many different pulley systems as you can (minimum of 4). For each, draw a detailed diagram and find the work done on the load and the work you did on the machine (work out and work in). We'll talk about anything significant you noticed on Wednesday.

Hint: you should notice something significant :)

Friday, 10/17: Teacher is sick!

I'm out for the day ladies and gents. I left a crossword puzzle and a work problem for the sub, plus some extra credit problems. The crossword and work problem are for a grade! Due Monday!

Good luck at Flowing Wells tonight!

Thursday, 10/16: Work and Power

You'll have to talk about these subjects with classmates; I started getting sick today and had to cease. I'll probably be out tomorrow.

Wednesday, 10/15: Still More Momentum!

Today we went over the back of Conceptual Development 7-1 and worked on these ranking tasks:











These are due on Friday, 10/17. Tomorrow: Energy!

Tuesday, 10/14: More Momentum!

We worked with momentum some more today. First we went through a bellwork problem that is very similar to #3 on yesterday's homework:







Then we worked on and corrected the front of Conceptual Development 7-1:












The back of Conceptual Development 7-1 is homework:

Monday, 10/13: Momentum and Impulse

Here are the partial notes for today. These are not complete! Nothing is better than actually being in class.

Due 10/14: HW: Momentum and Impulse

1. a. Which has a greater mass, a heavy truck at rest or a rolling skateboard?
b. Which has greater momentum?
2. When the force of impact on an object is extended in time, does the impulse increase or decrease?
3. In terms of impulse and momentum, why are air bags in automobiles a good idea? Explain thoroughly.

Wednesday, 10/8: Collisions

Today we looked at three collisions of carts on an air track. Before each demo, we drew a "before" diagram and a predicted "after" diagram. Then we watched the collision and drew what actually happened. The notes at the end show only the actual before and after diagrams.

Collision 1: Two carts of equal mass collide elastically. Cart one (m1) has some initial velocity to the right. Cart two (m2) is initially at rest. What will happen?


Collision 2: Two carts of equal mass collide elastically. Cart one (m1) has some initial velocity to the right. Cart two (m2) has a greater initial velocity to the left. What will happen?


Collision 3: Two carts of unequal mass collide inelastically. Cart one (m1) has some initial velocity to the right. Cart two (m2) is initially at rest. What will happen?


Here are the notes. Click to enlarge.

Tuesday, 10/7: Test 2!

Test 2 covers forces and Newton's Laws of Motion. There will be an alternate test for absences, but no make up test for poor grades.

Monday, 10/2: Guest Speaker on Nuclear Energy

Today Electrician's Mate 1st Class Jesse Shepard gave a presentation about nuclear science and energy. Awesome!

Remember: Test tomorrow!

Test 2 Review Answers

Test 2 Review Answers – not all answers are complete; this is just to check yourself.
1.Units= Newtons (N)
2.Units= kilograms (kg)
3.Weight = 250 N
4.25N
5.5N
6.Mass = inertia = hard to change motion (direction)
7.Both
8.Friction
9.Check your notes
10Notes, F=ma
11.½
12.P = F/A
13.Standing
14.No
15.Less area=more pressure with smaller force
16.Right
17.a. 600N down, b. 600N up; floor, c. 120N right, d. 120N right, e. 2 m/s2 right
18.same; bicycle
19.yes. Same
20.forces: team on rope, rope on team, team on ground, ground on team
21.large mass means small acceleration
22.Newton’s 3rd

Please go back and look at bellworks, homeworks, and notes.

Remember, you are allowed one side of one 3x5 inch notecard for use on the test.

Test 2 Review

These problems are good examples of problems that will appear on the test. All returned homework is also fair game. This review is not for a grade.

1. What is a force? What are the standard units of force? Give an example of a force.
2. What is mass? What are the standard units of mass?
3. What is weight? Find the weight of a 25 kg boulder on Earth.
4. Forces of 10N and 15N act on an object in the same direction. What is the net force?
5. Forces of 10N and 15N act on an object in opposite directions. What is the net force?
6. If an elephant is chasing you, its enormous mass seems very threatening. But if you zigzagged, the elephant’s mass would be to your advantage. Why?
7. Does the law of inertia apply to objects at rest, moving objects, or both? Support your answers with examples.
8. The law of inertia states that no force is needed to maintain motion. Why, then, do you have to keep pedaling your bicycle to keep it going?
9. State Newton’s 1^st Law.
10. State Newton’s 2^nd Law in words and in the form of an equation.
11. Suppose a shopping cart is being accelerated by a certain net force. If a load is dumped into the cart so its mass is doubled, by how much does the acceleration change?
12. Distinguish between force and pressure.
13. Which produces more pressure on the ground: a person standing up or the same person lying down? Explain.
14. If an object has no acceleration (a=0), can you say that no forces are acting on it? Explain and draw a free body diagram as an example.
15. Why does a sharp knife cut better than a dull knife?
16. A crate is pushed across the floor to the left. Which way does the friction force act on the crate?
17. A 60 kg student slides to the left across the linoleum floor in his socks.
1. What is the weight of the student?
2. What is the normal force on the student? What causes this normal force?
3. If the coefficient of kinetic friction is 0.2, what is the force of friction on the student?
4. Draw a free body diagram of the student and find the net force on the student.
5. Find the acceleration of the student.
18. If a bicycle and a truck have a head-on collision, upon which vehicle is the impact force greater? Which vehicle has the greatest change in its motion? Defend your answers.
19. We know that the Earth pulls on the Moon. Does the Moon also pull on the Earth? If so, which pull is stronger?
20. Draw a picture of two teams playing tug-of-war. Include all forces involved. What determines who wins?
21. When you push off the ground (jump up), the Earth really does recoil downward. Why isn’t this motion of the world noticed?
22. If you walk on a log that is floating in the water the log moves backward. Why?

Thursday, 10/2

Today we worked through a bellwork problem very similar to the friction homework assigned on Tuesday (9/30). Whatever time was left in the period was given over to finishing any work not yet turned in.

Due 10/2: HW: Pressure

A. Why do you want to spread yourself flat on thin ice?
B. A woman is wearing stiletto high heels with a surface area of 0.0001 square meters. Find the pressure exerted by the heel of her shoe if she weighs 50 N.
C. An elephant's feet have a surface area of 1 square meter. Find the pressure exerted if the elephant has a weight of 1000 N.
D. Would you rather have the woman in stilettos or the elephant step on your foot? Why?

Wednesday, 10/1: Pressure

Today we saw a demonstration and took a few notes. Click thumbnail to enlarge. And do the homework!