# HW Duep. 672 #1-7 – turn it in!!! HW tonightWorksheet on your way out the door – worth 11 pts, 1 pt per problem Do Now Take a study guide & clicker LOOK.

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HW Duep. 672 #1-7 – turn it in!!! HW tonightWorksheet on your way out the door – worth 11 pts, 1 pt per problem Do Now Take a study guide & clicker LOOK AT THE GRAPHIC ORGANIZER ON THE BOARD!!! (Take a picture/ put it in your notes – it’s important!!) Concept Development – do #1-3!

Concept Development Popcorn 1-3! We will do #4-7 together

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.Work, energy 2.Work, power 3.Momentum, energy 4.Momentum, work

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.Half as much 2.Twice as much 3.Three times as much 4.Nine times as much

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.lifting 10 kg a vertical distance of 2m B.lifting 5kg a vertical distance of 4m C.same work in both cases

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** Check Question! A.20 Joules B.20 Watt C.200 Joules D.200 Watts

4. How much work is done on an object when a force of 10N pushes it a distance of 10m? A.1 Joule B.1 Watt C.100 Joules D.100 Watts

5a. How much power is required to do 100J of work on an object in 1 second? A.1 Joule B.1 Watt C.100 Joules D.100 Watts

5b. How much power is required to do 100J of work on an object in 0.5 second? 1.50 J 2.50 W 3.200 J 4.200 W

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 1 st 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.Directly 2.Inversely 3.I have no idea

Check Question!!! Time and Power are ___ proportional 1.Directly 2.Inversely 3.I have no idea

POPCORN! 6. What are the 2 main forms of Mechanical Energy? (1 person will give one, and a 2 nd 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.More than 100 J 2.Less than 100 J 3.100 J 4.Zero

7b. If you lift it 2x as high, what’s its PE? 1.Less than 100 J 2.100 J 3.More than 100 J, but less than 200 J 4.200 J 5.More than 200 J 6.Zero

Check Question!!! Grav. PE and Height are ___ proportional 1.Directly 2.Inversely 3.I have no idea

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.More than 200 J 2.Less than 200 J 3.200 J 4.Zero

CHECK QUESTION 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 if there IS air resistance? 1.More than 200 J 2.Less than 200 J 3.200 J 4.Zero

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

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

KE is 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.The same (50 J) 2.More than 50 J 3.Less than 50 J

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 ONLY Which 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 J 22. Work = 1100 J; PE = 1100 J 23. 550 W PAGE 672 1.500 J 2.150 J 3.150 J 4.50 W 5.80 J 6.420 J 7.420 J When done… Please review the 8.3 – 8.6 GUIDED NOTES from last class (w/ the sand) in groups (check your work / solutions!) Then, complete the REST of the CONCEPT DEVELOPMENT. I will not be checking/collecting, but YOU will see ?s like this on your test – so it would be WISE to have this completed, corrected, and understood!

Return your clickers… TAKE A COPY OF THE HW!! 11 Points 1 point per problem For a few of the problems you will need to WRITE the question from your TEXT BOOK!!!

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