March 15 & 18

• Do Now: Take one and complete; take a clicker! Also, turn in your Ch 13 HW questions!

• Tonight’s HW: p. 181, #21 – 26, & 29; 32-33 . – Write full Q&A. – 2 points per problem– 18 points total.

• Today’s Objectives:– Complete the Do Now and clicker review of Do Now– Check and Correct Ch 12 notes– Fill out a self-assessment– Clicker Review of HW– If time, start tonight’s HW

See Do Now, front page…

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1. The farther star is ½ as massive as the closer star

2. The farther star is ¼ as massive as the closer star

3. The farther star is 2x as massive as the closer star

4. The farther star is 4x as massive as the closer star

See Do Now, back page… 1. Is weight a force?

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1. Yes2. No

2a. How would the gravitational force between a pair of planets be altered if:

The mass of one planet is doubled?

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1. Gravity is halved (1/2)2. Gravity is 1/43. Gravity is doubled (2x)4. Gravity is quadrupled (4x)

2b. How would the gravitational force between a pair of planets be altered if:

The planets are 2x as far apart?

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1. Gravity is halved (1/2)2. Gravity is 1/43. Gravity is doubled (2x)4. Gravity is quadrupled (4x)

2c. How would the gravitational force between a pair of planets be altered if:

The planets are 3x as far apart?

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1. Gravity is 1/32. Gravity is 1/93. Gravity is 3x4. Gravity is 9x

2d. How would the gravitational force between a pair of planets be altered if:

The masses of both planets are doubled AND they are 2x as far apart?

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1. Gravity is 2x2. Gravity is ½3. Gravity is 4x4. Gravity is ¼5. Gravity is 8x6. Gravity is 1/8 7. Gravity is the same

3a. What would happen to YOUR WEIGHT if:The masses of both you and earth are doubled?

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1. Gravity is 2x2. Gravity is ½3. Gravity is 4x4. Gravity is ¼5. Gravity is 8x6. Gravity is 1/8 7. Gravity is the same

3b. What would happen to YOUR WEIGHT if:You are 10x as farther away from the center of

Earth?

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1. Gravity is 20x2. Gravity is 1/203. Gravity is 10x4. Gravity is 1/105. Gravity is 100x6. Gravity is 1/1007. Gravity is the same

3c. What would happen to YOUR WEIGHT if: The mass of Earth is doubled AND you are 2x as

far?

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1. Gravity is 2x2. Gravity is ½3. Gravity is 4x4. Gravity is ¼5. Gravity is 8x6. Gravity is 1/8 7. Gravity is the same

4. Did you use a different process to answer #2-3

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1. Yes2. No3. Not sure

ACTIVITY GOALS:–Activity to check Monster Ch 12 notes–Keys at each lab bench; see white board for

the amount of time– If you have questions put them on your Q & A sheet, and SEE A TEACHER!**Answers mean NOTHING if you

don’t ‘get’ WHY the answer is what it is!!! PROCESS (discussion/ rationale) is more important than PRODUCT (answer)**

CHAPTER 12:Homework Questions #8-13

Page 180

8. What did Newton discover about gravity?

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1. That gravity exists2. That gravity is

different on Earth than it is in other parts of the universe

3. That gravity is universal and follows a simple mathematical formula

9. What does the small value of G tell us about the force of gravity?

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1. That gravity exists2. That gravity a strong

force3. That gravity is a

weak force4. G doesn’t tell us

anything about gravity

10. What 2 masses and 1 distance determine your weight? (graded)

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1. A 1 kilogram mass, earth’s mass, distance between you and center of earth

2. A 1 kilogram mass, earth’s mass, and 9.8 Newtons

3. A lead mass, a mercury flask, and the distance between them

4. Your mass, earth’s mass, distance between you and center of earth

11. In what way is gravity reduced with distance from Earth?

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1. Gravity is not affected by distance

2. Directly proportional (double the distance, double gravity)

3. Inversely proportional (double the distance, ½ gravity)

4. Inverse square (double the distance, ¼ the gravity)

12. Difference in your weight if you were 5x father from the center of Earth? 10x farther?

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1. Weigh 5x as much; 10x as much2. Weigh 1/5 as much; 1/10 as much3. Weigh 10x as much; 20x as much4. Weigh 1/10 as much; 1/20 as much5. Weigh 10x as much; 100x as much6. Weigh 1/25 as much; 1/100 as much

13. What makes Earth round?

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1. Magic2. Rotation3. Perturbation 4. Gravity and surface tension

CHAPTER 13:Homework Questions

#2-5, 9-10, 19-20 (p. 196)

2. Which statement is correct:

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1. A distant rocket interacts with the mass of earth

2. A distant rocket interacts with the gravitational field of earth

3. Both are correct4. Neither are correct

3. How does the gravitational field at earth compare with the acceleration of free fall?

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1. Numerically equal2. Numerically different

4. On what does acc. of gravity on diff. planets depend?

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1. Earth’s mass, other planet's mass, and distance b/t earth and other planet

2. Earth’s mass, your mass, and distance b/t earth and other planet

3. Earth’s mass, other planet's mass, and distance b/t you and other planet

4. G, m, and r same formulas as Earth!

5. How does Earth’s gravity vary with increasing distance?

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1. Gravity is the same; is not affected by distance

2. More gravity3. Less gravity

9. Does your apparent weight change when you ride an elevator moving at a constant speed? An accelerating elevator? Explain

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1. No; no2. Yes; yes3. Yes; no4. No; yes

10. How does the support force of a floor you stand on relate to weight?

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1. Support force > weight2. Support force < weight3. Support force = weight4. None of the above

19. Black dwarf vs. black hole?

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1. Dwarf: small, burned out star; Black hole: collapsed giant star

2. Black hole : small, burned out star; Dwarf: collapsed giant star

3. They are the same thing

20. Why would Earth not be sucked into the sun If it became a black hole?

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1. Mass is different 2. Mass remains the same 3. Magic4. This is not true- earth would

definitely be sucked into the sun!

• The gravitational field NEAR the black hole is enormous. But the field BEYOND the original radius of the star is no different after collapse than before…in other words, no different as a black hole than as a star. – The amount of mass has not

changed, so there is no change in the field at any point beyond this distance.

– If our sun was to turn into a black hole today, Earth would orbit as usual since it is outside the radius of the original sun

• The gravitational field strength near a giant star that collapses to become a black hole is the same before collapse (left) and after collapse (right).

• It is only when you get CLOSE that gravity starts to change.– If you get within a distance smaller than the original radius

of the star, gravity starts to change. This “edge” is called the event horizon – once you cross it, nothing can escape…not even light

HW

• If time remains, you may being your HW for tonight

• Tonight’s HW: p. 181, #21 – 26, & 29; 32-33 . – Write full Q&A. – 2 points per problem– 18 points total.

3rd Marking Period Project – Take a Rubric for Space Exploration Public

Service Announcement– You may work in groups of 1-4– You may have time to being after your Test– You will get the day after spring break to

complete–Due April 11 & 12 at START of your class–Questions?