HW Due p. 672 #1-7 – turn it in!!! HW tonight

p. 120-121#24 – 2731, 34 – 3537, 41 – 42

Do Now

Page 121, #45 – in your notes, complete this problem! May collaborate with peers… think carefully! Use the info on the board to guide your thinking.

10 points1 point per problem!

Write the FULL Q&A, or reword it in your answer !!!

HW Due p. 672 #1-7 – turn it in!!! HW tonight

p. 120-121#24 – 2731, 34 – 3537, 41 – 42

Do Now

Page 121, #45 – in your notes, complete this problem! May collaborate with peers…

CHECK by reading p. 108, focusing on Fig. 8.5 and its description…

10 points1 point per problem!

Write the FULL Q&A, or reword it in your answer !!!

Do Now Extension:

• What did you learn from the DO NOW that will help you when you start driving?

• You're driving on Pond Road (25 mph). Then, you drive on 195 (65 mph). On which road should you leave more STOPPING DISTANCE between you and the car in front of you? Why?

Goals for Today1. Check your HW!!! – Check the book HW using clickers • #1-13, 21-23 p.119• #1-7 p. 672

2. IN GROUPS:• Check the guided notes up to the boxed

questions • Need help? ASK! • Complete the ***Boxed Questions on last

week’s notes***

Take out your book HW• #1-4• #5, 21-23• #6-13(^^^ all from page 119 ^^^)

• And p. 672, #1-7 (last night’s HW – you just got this back)

***Unless otherwise stated, assume NO:- Friction- Air resistance- Sound - Etc.

1. What do we call the quantity force times distance, and what quantity can it change?

1 2 3 4

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1. Work, energy2. Work, power3. Momentum,

energy4. Momentum, work

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10

2. Work is required to lift a barbell. How many more times work is required to lift the same barbell 3 times as high?

1 2 3 4

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1. Half as much2. Twice as much3. Three times as

much4. Nine times as

muchCountdown

10

3. Which requires more work: lifting a 10 kg mass a vertical distance of 2m, or lifting a 5kg mass a vertical distance of 4m?

A. B. C.

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A. lifting 10 kg a vertical distance of 2m

B. lifting 5kg a vertical distance of 4m

C. same work in both cases

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10

Check Question!Calculate the ACTUAL work done in lifting…

– a 10 kg mass a vertical distance of 2m– a 5kg mass a vertical distance of 4m

CAREFUL!W = ΔE

Fd= Δ(mgh)Are you given the FORCE (weight), or the MASS?

Which equation pertains to this problem?

Calculate the ACTUAL work done in lifting… - a 10 kg mass a vertical distance of 2m - a 5kg mass a vertical distance of 4m

**They are the same answer**

A. B. C. D.

0% 0%0%0%

Check Question!

A. 20 JoulesB. 20 WattC. 200 JoulesD. 200 Watts

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10

4. How much work is done on an object when a force of 10N pushes it a distance of 10m?

A. B. C. D.

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A. 1 JouleB. 1 WattC. 100 JoulesD. 100 Watts

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10

5a. How much power is required to do 100J of work on an object in 1 second?

A. B. C. D.

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A. 1 JouleB. 1 WattC. 100 JoulesD. 100 Watts

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10

5b. How much power is required to do 100J of work on an object in 0.5 second?

1 2 3 4

0% 0%0%0%

1. 50 J2. 50 W3. 200 J4. 200 W

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10

IMPORTANT INFO!

If you have a scenario with the…• SAME work…• But HALF the time…• Then there is TWICE the power!!!

Consider this analogy…1996 Dodge Neon (my 1st car!) vs. 2014 Corvette Stingray

• Which can go from 0-60 mph in LESS time? • Which is more powerful?

IMPORTANT INFO!

If you have a scenario with the…• SAME work…• But HALF the time…• Then there is TWICE the power!!!

Check Question!!!Work and Power are __proportional

1 2 3

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1. Directly2. Inversely3. I have no idea

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Check Question!!!Time and Power are ___ proportional

1 2 3

0% 0%0%

1. Directly2. Inversely3. I have no idea

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10

POPCORN!

6. What are the 2 main forms of Mechanical Energy?

(1 person will give one, and a 2nd person will give the other)

7a. If you do 100 J of work to elevate a bucket of water, what is its grav. PE relative to its starting point?

1 2 3 4

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1. More than 100 J2. Less than 100 J3. 100 J4. Zero

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10

7b. If you lift it 2x as high, what’s its PE?

1 2 3 4 5 6

0% 0% 0%0%0%0%

1. Less than 100 J2. 100 J3. More than 100 J, but

less than 200 J4. 200 J5. More than 200 J6. Zero

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10

Check Question!!!Grav. PE and Height are ___ proportional

1 2 3

0% 0%0%

1. Directly2. Inversely3. I have no idea

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10

8. A boulder is raised above the ground so that its grav. PE is 200 J (relative to the ground). Then it’s dropped. What’s its KE the INSTANT just before hitting the ground?

1 2 3 4

0% 0%0%0%

1. More than 200 J2. Less than 200 J3. 200 J4. Zero

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10

CHECK QUESTIONA boulder is raised above the ground so that its grav. PE is 200 J (relative to the ground). Then it’s dropped. What’s its KE the INSTANT just before hitting the ground if there IS air resistance?

1 2 3 4

0% 0%0%0%

1. More than 200 J2. Less than 200 J3. 200 J4. Zero

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10

9a. Suppose an automobile has 2000 J of kinetic energy. When it moves a twice the speed, what will be its kinetic energy?

1 2 3 4 5 6

0% 0% 0%0%0%0%

1. The same (2000 J)2. 2x as much (4000 J)3. 3x as much (6000 J)4. 4x as much (8000 J)5. 6x as much (12,000 J)6. 9x as much (18,000 J)

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10

9b. Suppose an automobile has 2000 J of kinetic energy. What’s its kinetic energy at three times the speed?

1 2 3 4 5 6

0% 0% 0%0%0%0%

1. The same (2000 J)2. 2x as much (4000 J)3. 3x as much (6000 J)4. 4x as much (8000 J)5. 6x as much (12,000 J)6. 9x as much (18,000 J)

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10

KEis directly proportional

to the SQUARE of the velocity!

10. What will be the kinetic energy of an arrow having a potential energy of 50 J after it is shot from a bow?

1 2 3

0% 0%0%

1. The same (50 J)2. More than 50 J3. Less than 50 J

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10

POPCORN

11. What does it mean to say that in any system the total energy score stays the same?

POPCORN

11. What does it mean to say that in any system the total energy score stays the same?

Energy is conserved.

POPCORN

12. In what sense is energy from coal actually solar energy?

POPCORN

12. In what sense is energy from coal actually solar energy?

LONG ANSWER: Coal is formed from organic material. Organic materials (plants, the animals that eat plants, and the animals that eat animals that eat plants) get their energy from the sun.

SHORT ANSWER: Coal is made from tiny dead organisms that needed the sun to be alive at one time.

POPCORN

13. How does the amount of work done on an automobile by its engine relate to the energy content of the gasoline?

POPCORN

13. How does the amount of work done on an automobile by its engine relate to the energy content of the gasoline?

It is less than the energy contained in the gasoline. An automobile engine is not 100% efficient.

(Some of the gas energy powers the car…but some is transferred into heat, sound, etc… TOTAL ENERGY stays the same, but that sum is made of diff. types of Potential and Kinetic energy!)

ANSWERS ONLYWhich doesn’t help you if you don’t know HOW to fix/complete the

problem!!!Check your work… get help from a peer or teacher if needed!!!

PAGE 119-120 21. 70 J22. Work = 1100 J; PE = 1100 J23. 550 W

PAGE 672 1. 500 J2. 150 J3. 150 J4. 50 W5. 80 J6. 420 J7. 420 J

When done…Please review the 8.3 – 8.6 GUIDED NOTES from last week (w/ the sand) in groups (check your work / solutions!) Then, complete the BOXED QUESTIONS in those notes. I will not be checking/collecting, but this is a study tool for your test!

CHECK QUESTIONS!

• This is our exit.• When done, return your clicker!

Can energy ever be created?

1 2 3

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1. Yes2. No3. Sometimes

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10

Can energy ever be destroyed?

1 2 3

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1. Yes2. No3. Sometimes

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Does an object with momentum always have energy?

1 2

0%0%

1. Yes2. No

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10

Does an object with energy always have momentum?

1 2 3

0% 0%0%

1. Yes2. No

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10

If a mouse and an elephant both run with the same kinetic energy, can you say which is running faster?

1 2 3

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1. The mouse2. the elephant3. Not enough info

to say

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Is it possible for an object to have BOTH PE & KE (simultaneously)?

1 2 3

0% 0%0%

1. Yes2. No 3. Not enough info

to say

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10

Return your clickers…don’t forget tonight’s HW!

HW tonight

p. 120-121#24 – 2731, 34 – 3537, 41 – 42

10 points1 point per problem!

Write the FULL Q&A, or reword it in your answer !!!