Newton’s Law of Gravity

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Slide 1

Slide 2

Bit of Administration ….

6-Week Test

Monday, March 1, 7:15-8:30, 3425 Sterling

56 multiple choice questions

2/3 conceptual use of the material

1/3 recall

All material in lecture, discussion, homeworks

through today; readings on that material

Review Session

Sunday, February 29, 6:30-7:30, 3425 Sterling

Will answer questions, no new presentations

Slide 3

Newton’s Law of Gravity

1

2

Fg

Fg

M1 = Mass of object 1 (grams)

M2 = Mass of object 2 (grams)

D = Distance between objects (cm)

G = 6.67x10-8 cm3/sec2/gm

Slide 4

Newton’s Law of Gravity

Galileo’s Experiment

Lead

Wood

Earth

Fg,lead

Fg,wood

alead

awood

Slide 5

Newton’s Law of Gravity

Mass = Amount of Material

Weight = Force Due to Gravity

Slide 6

On much of the European continent, the heft of people is called their mass and measured in kilograms. Like in the United States, they measure themselves by stepping on a bathroom floor scale.

True or False: Strictly speaking, when they step on the scale they are not measuring their mass but instead are measuring their weight.

A) True

B) False

C) Its debatable

ConcepTest!

Slide 7

Newton’s Law of Gravity

“Weightlessness”

200 lbs

Slide 8

Newton’s Law of Gravity

?

Slide 9

After jumping off the building (and before landing!), what weight will the scale read?

A) 0 pounds

B) 20 pounds

C) 200 pounds

D) 300 pounds

ConcepTest!

Slide 10

Newton’s Law of Gravity

“Weightlessness” - No such thing; would imply no gravity

- A consequence of all object in free fall

at same acceleration

0 lbs

Slide 11

Newton’s Law of Gravity

Orbits

Slide 12

Newton’s Law of Gravity

Orbits

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