Hi folks,
Today we continued our investigation into energy and work. We have begun to take a look at simple machines and how they relate to the concept of work. We used pulleys to discover the inverse relationship between distance and force.
Most of today was spent reviewing problems and doing our pulley lab so there will be no recording this week.
For homework this week:
Read the pulley chapter in the book.
Also, answer the following questions.
1. With the pulleys, how did work out relate to work in?
2. What relationship did force have in regards to distance as you worked with the pulleys?
3. As you increased the number of pulleys, what effect did that have on the effort force? What effect did it have on the effort distance?
4. a. If you were lifting a load that required a force of 10N with one pulley, what effort force would be required?
b. Same question, but now you're using 2 pulleys?
c. How about 10 pulleys?
5. a. If you were lifting that load 1 meter, what would the work in distance be for one pulley?
b. 2 pulleys?
c. 10 pulleys?
Monday, January 30, 2017
Make up test for Physics
Hi folks,
It looks like we need a bit more work with some of these problems so I'm going to assign a take home quiz. Feel free to use your notes for this. It will be worth 20 points just like a normal quiz. Please use this to attempt to master these problems. They will certainly be back to haunt you on the final if not sooner.
Good Luck!
Jim Mueller
It looks like we need a bit more work with some of these problems so I'm going to assign a take home quiz. Feel free to use your notes for this. It will be worth 20 points just like a normal quiz. Please use this to attempt to master these problems. They will certainly be back to haunt you on the final if not sooner.
Good Luck!
Jim Mueller
Wednesday, January 25, 2017
Tuesday, January 24, 2017
Recording of 1/23 Physics class - Work and "Punt the football" problem
Sorry about that last email. I sent the wrong recording. Here's the one for yesterday's class.
Monday, January 23, 2017
1/23 Physics class and homework due 1/30
Hi folks,
Last week we did a nice conceptual overview of what energy is and this week we got a bit more into the nitty gritty and mathematics behind energy. We introduced the concept that energy is the ability to do work and that work is equal to force times distance. To make that more concrete, we went outside and pushed my car again. This time, however, we measured the amount of force it took to move the car and measured how much time it took to move it. Using those measurements we calculated the energy it took for us to move the car and we found how many Watts and how much horsepower we used.
In my opinion the text that we're using goes into too little detail on energy. I'm including my Energy eBook to help supplement the text
Homework due next is to
Read the Defining Energy chapter in the eBook
In the Conceptual Physics text book do Plug and Chug Pg 120 #'s 1 and 3
And Think and Solve # 2, 4
I've included the answers for the problems below.
Plug and Chug
1. 20 x 3.5 = 70J
3. First find work from question #2.
500N x 2.2m = 1100J
Then take 1100 J/2 = 550W
Think and Solve
2. Twice the power would be 1/2 the time. So the answer is 5 s.
4. So the car starts with 40,000,000 J. If the car is 25% fuel efficient that means that only 25% of that goes to making the car move so only 10,000,000 of the energy is used. So now, plug n chug.
10,000,000 = 1000 x D
10,000 m = D Or 10 Km
Last week we did a nice conceptual overview of what energy is and this week we got a bit more into the nitty gritty and mathematics behind energy. We introduced the concept that energy is the ability to do work and that work is equal to force times distance. To make that more concrete, we went outside and pushed my car again. This time, however, we measured the amount of force it took to move the car and measured how much time it took to move it. Using those measurements we calculated the energy it took for us to move the car and we found how many Watts and how much horsepower we used.
In my opinion the text that we're using goes into too little detail on energy. I'm including my Energy eBook to help supplement the text
Homework due next is to
Read the Defining Energy chapter in the eBook
In the Conceptual Physics text book do Plug and Chug Pg 120 #'s 1 and 3
And Think and Solve # 2, 4
I've included the answers for the problems below.
Plug and Chug
1. 20 x 3.5 = 70J
3. First find work from question #2.
500N x 2.2m = 1100J
Then take 1100 J/2 = 550W
Think and Solve
2. Twice the power would be 1/2 the time. So the answer is 5 s.
4. So the car starts with 40,000,000 J. If the car is 25% fuel efficient that means that only 25% of that goes to making the car move so only 10,000,000 of the energy is used. So now, plug n chug.
10,000,000 = 1000 x D
10,000 m = D Or 10 Km
Tuesday, January 17, 2017
Monday, January 16, 2017
1/16 Physics update and homework due 1/23
Hi folks
We have finished our study of Newton's Laws and mechanics and have started our energy block today. We discussed how we perceive energy using our energy "antennae", our ears, eyes and skin. We also discussed how energy is like a phantom. It's invisible until it interacts with matter, it changes forms and it can neither be created nor destroyed.
For homework this week:
Study the "quiz" we did today in class. I've included a copy. Next week I will give another quiz that won't be the same as this one, but it will use the same concepts. Don't forget that to figure out acceleration you must use the time that the object is acceleration ONLY! So for today's quiz, you would only use the time that the fellow was flung in the slingshot. Not the entire time he was in the air.
Read chapter 8 pages 103- 119. (This will give you a brief overview of what we will be spending a lot of time on over the next few weeks. The book doesn't go into nearly the detail I think we need to spend on this topic.)
Do Review Questions 1 - 13 on page 119
We have finished our study of Newton's Laws and mechanics and have started our energy block today. We discussed how we perceive energy using our energy "antennae", our ears, eyes and skin. We also discussed how energy is like a phantom. It's invisible until it interacts with matter, it changes forms and it can neither be created nor destroyed.
For homework this week:
Study the "quiz" we did today in class. I've included a copy. Next week I will give another quiz that won't be the same as this one, but it will use the same concepts. Don't forget that to figure out acceleration you must use the time that the object is acceleration ONLY! So for today's quiz, you would only use the time that the fellow was flung in the slingshot. Not the entire time he was in the air.
Read chapter 8 pages 103- 119. (This will give you a brief overview of what we will be spending a lot of time on over the next few weeks. The book doesn't go into nearly the detail I think we need to spend on this topic.)
Do Review Questions 1 - 13 on page 119
Monday, January 9, 2017
1/9 Physics class and homework due 1/16
Hi folks,
Today we used just about every concept we've learned this year and applied our knowledge to the game of Angry Birds. We discovered the impulse, velocity, momentum and more of the different objects in the Angry Birds world. It was a very difficult challenge and folks really did a great job attacking the problems.
I've included the questions below in case you want to take a look at them. Here's a great write up of a fellow who did the same kind of a thing we did today. It's pretty interesting if you want to take a look. By the way, he calculates the slingshot to be 5 meters tall!
No recording this week since most of class was taken up by the activity.
Homework this week is a scavenger hunt. I want you all to find two examples of all the concepts written below.
Rules:
They must all be different.
They must all be photos taken with a camera (not images from the internet).
They can be things that you just come across or you can set up situations that exemplify the concept.
Write a sentence for each one indicating why that photo is an example.
Videos are allowed if you wish.
You can print out the photos to hand in or you can email them to me.
1. Newton's First Law
2. Newton's Second Law
3. Newton's Third Law
4. Momentum
5. Impulse
6. Acceleration
7. Inertia
Angry Birds Analysis
Some assumptions for you:
The time it takes the rubber band to hurl a bird is .05 sec. (This is the time of a pitch.)
The mass of the Red Bird is 6kg (the same as an eagle)
Gravity is normal 9.8 m/s2
Do # 8 first!!!!
1. What is the maximum horizontal velocity of an Angry Bird?
2. What is the maximum vertical velocity of the Angry Bird?
3. What is the maximum resulting velocity of the Bird?
4. Are all birds the same mass? How do you know?
5. What is the force of the rubber band?
6. What is the mass of a rock (be sure to describe what rock you're measuring)?
7. What is the impulse on the angry bird when it's fired.
8. What is the height of the sling shot?
9. Does the Blue Bird conserve momentum when it splits? How do you know?
10. What's the momentum of the Red bird?
11. Using Angry Birds give me one example of the following:
a) Newton's First Law
b) Newton's Second Law
c) Newton's Third Law
Angry Birds for Physics
Hi folks,
Just a reminder. If you can, please bring a version of the game Angry Birds to class today.
Safe travels everyone!
Jim Mueller
Just a reminder. If you can, please bring a version of the game Angry Birds to class today.
Safe travels everyone!
Jim Mueller
Tuesday, January 3, 2017
Monday, January 2, 2017
1/2 Physics update and homework due 1/9
Hi folks,
This week we discussed the concept of impulse and how it relates to momentum. To investigate this further, we shot spitballs to illustrate how the time of the force affects momentum.
We also did the famous egg drop experiment where the students had to design a vehicle that kept a raw egg safe from a 15 foot drop. There were some brilliant designs!
For homework this week:
1. In your own words, describe to me what shooting spitballs has to do with impulse?
2. Use the concept of impulse to explain why it's so important to follow through when doing some sort of a sporting activity.
3. During the egg drop activity, you used several strategies to try to keep your egg from breaking. List three of those strategies and tell me what they had to do with impulse and momentum.
Also, Do the following questions. (Answers below.)
1. A Denver Bronco is running towards the end zone at 11 m/s (25mph). A Pittsburg Steeler running directly behind him at 15 m/s (34mph) tackles him and causes him to fumble directly into the hands of another Steeler who runs it back for, the final seconds, game winning touchdown!!! If the Bronco weighs 127 kg (280lbs) and the Steeler weighs 136 kg (300 lbs), what is their velocity after impact and before hitting the ground? (Use metric #'s only. Others are there for reference.) (Check answer when finished below.)
2. Two train cars are moving towards each other along a track. One has a mass of 32,000 kg and is traveling at 3.5 m/s. The other has a mass of 23,000 kg and is traveling at 5 m/s. Assuming they stick together after impact, what is their final velocity? (Check answer when finished below.)
3. Describe throwing a bowling ball down the alley and knocking down all the pins as far as momentum transfer goes. Start with holding the ball and end with the last pin falling. Extra Credit: Show me the #'s and calculations.
AND
Use this websitehttp://phet.colorado.edu/sims/collision-lab/collision-lab_en.html to complete the following questions:
Please let me know if this website doesn't work for folks. It works fine for me but I'm not sure it will work for all of you.
Phet Momentum Homework
1. Click on the Advanced tab at the top of the window.
2. Click on "One Dimension" in the box to the upper right.
3. Click on the "Momenta Diagram" button in the upper right.
4. Click on the "Show Values" button in the upper right.
5. Set the speed of ball 2 to 0 (Drag the vector arrow for ball 2 until V = 0)
6. Notice the total momentum of both balls. (In the momenta box to the lower right)
7. Click play.
(Be sure you look at the numbers for the following questions before either ball bounces off the wall. If you wish, you can turn off "Reflecting Border" in the upper right corner.
8. How does the total momentum of the system after collision, compare to the total momentum before collision?
9. Now, make both balls have a mass of 1.5. What happens to their velocity after collision?
10. How about their total momentum before and after collision how do they compare?
11. Now click "Add Ball" at the bottom. This ball should have a mass of 2 and a velocity of 0. What is the total momentum?
12 Now click play, what is the total momentum after collision?
13. Click on the "Momenta Vectors" button in the bottom right.
14. Click on remove ball so that you only have 2 on the screen.
15. Notice the momentum vectors. Look carefully at the total momentum vector.
16. Click play. After collision how does the total momentum vector change?
17. Add a ball and do it again. Notice anything about the momentum vector now?
18. Please feel free to play with this. Add balls, try two dimensions, what ever you wish.
Answers to math problems.
1. MV of Bronco + MV of Steeler = Mass of both x velocity of both
(11m/s x 127Kg) +(15m/s x 136Kg) = 263 x Vf
1397 + 2040 =263v
13.1m/s = V
2. MV of car 1 + MV of car 2 = Mass of both x velocity of both
(32,000 x 3.5) + (23,000 x -5) = 55,000 x Vf (Notice that the second speed is negative due to the opposite direction of travel. I assigned moving right as positive and moving left as negative.)
112,000 + -115000 = 55,000 Vf
-3000 = 55,000 Vf
-.06 m/s = Vf (The cars will be moving slightly to the left after impact.
This week we discussed the concept of impulse and how it relates to momentum. To investigate this further, we shot spitballs to illustrate how the time of the force affects momentum.
We also did the famous egg drop experiment where the students had to design a vehicle that kept a raw egg safe from a 15 foot drop. There were some brilliant designs!
For homework this week:
1. In your own words, describe to me what shooting spitballs has to do with impulse?
2. Use the concept of impulse to explain why it's so important to follow through when doing some sort of a sporting activity.
3. During the egg drop activity, you used several strategies to try to keep your egg from breaking. List three of those strategies and tell me what they had to do with impulse and momentum.
Also, Do the following questions. (Answers below.)
1. A Denver Bronco is running towards the end zone at 11 m/s (25mph). A Pittsburg Steeler running directly behind him at 15 m/s (34mph) tackles him and causes him to fumble directly into the hands of another Steeler who runs it back for, the final seconds, game winning touchdown!!! If the Bronco weighs 127 kg (280lbs) and the Steeler weighs 136 kg (300 lbs), what is their velocity after impact and before hitting the ground? (Use metric #'s only. Others are there for reference.) (Check answer when finished below.)
2. Two train cars are moving towards each other along a track. One has a mass of 32,000 kg and is traveling at 3.5 m/s. The other has a mass of 23,000 kg and is traveling at 5 m/s. Assuming they stick together after impact, what is their final velocity? (Check answer when finished below.)
3. Describe throwing a bowling ball down the alley and knocking down all the pins as far as momentum transfer goes. Start with holding the ball and end with the last pin falling. Extra Credit: Show me the #'s and calculations.
AND
Use this websitehttp://phet.colorado.edu/sims/collision-lab/collision-lab_en.html to complete the following questions:
Please let me know if this website doesn't work for folks. It works fine for me but I'm not sure it will work for all of you.
Phet Momentum Homework
1. Click on the Advanced tab at the top of the window.
2. Click on "One Dimension" in the box to the upper right.
3. Click on the "Momenta Diagram" button in the upper right.
4. Click on the "Show Values" button in the upper right.
5. Set the speed of ball 2 to 0 (Drag the vector arrow for ball 2 until V = 0)
6. Notice the total momentum of both balls. (In the momenta box to the lower right)
7. Click play.
(Be sure you look at the numbers for the following questions before either ball bounces off the wall. If you wish, you can turn off "Reflecting Border" in the upper right corner.
8. How does the total momentum of the system after collision, compare to the total momentum before collision?
9. Now, make both balls have a mass of 1.5. What happens to their velocity after collision?
10. How about their total momentum before and after collision how do they compare?
11. Now click "Add Ball" at the bottom. This ball should have a mass of 2 and a velocity of 0. What is the total momentum?
12 Now click play, what is the total momentum after collision?
13. Click on the "Momenta Vectors" button in the bottom right.
14. Click on remove ball so that you only have 2 on the screen.
15. Notice the momentum vectors. Look carefully at the total momentum vector.
16. Click play. After collision how does the total momentum vector change?
17. Add a ball and do it again. Notice anything about the momentum vector now?
18. Please feel free to play with this. Add balls, try two dimensions, what ever you wish.
Answers to math problems.
1. MV of Bronco + MV of Steeler = Mass of both x velocity of both
(11m/s x 127Kg) +(15m/s x 136Kg) = 263 x Vf
1397 + 2040 =263v
13.1m/s = V
2. MV of car 1 + MV of car 2 = Mass of both x velocity of both
(32,000 x 3.5) + (23,000 x -5) = 55,000 x Vf (Notice that the second speed is negative due to the opposite direction of travel. I assigned moving right as positive and moving left as negative.)
112,000 + -115000 = 55,000 Vf
-3000 = 55,000 Vf
-.06 m/s = Vf (The cars will be moving slightly to the left after impact.
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