ASTR-1010ASTR-1010Planetary AstronomyPlanetary Astronomy

Day - 15

ClassAction StuffClassAction Stuff

• Gravity Stuff

• Splash page warm up

AnnouncementsAnnouncements

Homework Chapter 3: Due Wednesday Feb. 24

Smartworks Chapters 4 & 5 are also posted

Exam 2 will cover chapters 3, 4, & 5

There is a new discussion board question posted.

Ranking Task (Kepler’s laws) due now.

Ranking Task (Gravity) due Monday at classtime.

1st quarter observing night: Either Monday or Wednesday …based on weather.

Isaac Isaac Newton Newton (1642 – (1642 – 1727)1727)

The Baddest The Baddest Dead White Dead White Guy of Them Guy of Them

AllAll

Isaac Newton (1642 – 1727)Isaac Newton (1642 – 1727) is known foris known for

1. First observations of the sun

2. First sun centered scientific model of the solar system or universe

3. Being the world’s best naked-eye astronomer

4. Creating first a theoretical model to explain planetary motions

5. Creating first theoretical model for explaining gravity and …..

Isaac Newton (1642 – 1727)Isaac Newton (1642 – 1727) is known foris known for

1. First observations of the sun

2. First sun centered scientific model of the solar system or universe

3. Being the world’s best naked-eye astronomer

4. Creating first a theoretical model to explain planetary motions

5. Creating first theoretical model for explaining gravity and …..

Isaac Newton Isaac Newton formulated formulated

three laws of three laws of motion and the motion and the

law of law of gravitation – gravitation – these laws these laws

describe the describe the motion of our motion of our physical worldphysical world

Newton’s Three Laws of Newton’s Three Laws of MotionMotion

First Law - A body remains at rest or moves in a straight line at a constant speed unless acted upon by an outside (net) force.

Second Law - (net) Force = mass x acceleration

Third Law - Whenever one body exerts a force on a second body, the second body exerts an equal and opposite force on the first body.

ClassAction StuffClassAction Stuff

• Gravity Stuff

• Newton Law animation

• Gravity calculator

• Splash pages 11-23

Newton’sNewton’s FirstFirst LawLaw

• A body remains at rest or moves in a straight line at a constant speed unless acted upon by an outside (net) force.

• A rockets will coast in space along a straight line at constant speed.

• A hokey puck glides across the ice at constant speed until it hits something

Newton’sNewton’s SecondSecond Law of Law of MotionMotion

• (net)Force = mass x acceleration or Fnet = m x a

• Acceleration is the rate of change in velocity – or how quickly your motion is changing.

• Three accelerators in your car!!

Newton’sNewton’s ThirdThird Law of MotionLaw of Motion

• Whenever one body exerts a force on a second body, the second body exerts an equal and opposite force on the first body.

• Don’t need a rocket launch pad!• The Bug and the Windshield – who is

having the worse day?

Newton’s Three Laws of Newton’s Three Laws of Motion - ReviewMotion - Review

First Law - A body remains at rest or moves in a straight line at a constant speed unless acted upon by an outside (net) force.

Second Law - (net) Force = mass x acceleration

Third Law - Whenever one body exerts a force on a second body, the second body exerts an equal and opposite force on the first body.

Newton’s Law of GravitationNewton’s Law of Gravitation• Newton’s law of gravitation states: Two

bodies attract each other with a force that is directly proportional the product of their masses and is inversely proportional to the square of the distance between them.

2

21

d

mGmFgrav

What the ….? I thought I understood gravity?

Isaac Newton (1642 – 1727)Isaac Newton (1642 – 1727) --

1.Probably died a virgin

2.Was a priest and Lawyer

3.Had artificial wooden and silver noses

4.Probably died of Mercury poisoning

5.Rumored to have died when his bladder burst

6.Was blind at the time of his death

7.Was labeled a heretic by the church

Isaac Newton (1642 – 1727)Isaac Newton (1642 – 1727) --

1. Probably died a virgin

2. Was a priest and Lawyer

3. Had artificial wooden and silver noses

4. Probably died of Mercury poisoning

5. Rumored to have died when his bladder burst

6. Was blind at the time of his death

7. Was labeled a heretic by the church

Newton’s Law of GravitationNewton’s Law of Gravitation• To figure out the gravitational force just

multiply the mass of the two things together then divide by the distance they are apart (squared).

2

21

d

mGmFgrav

m1

m2

d

Newton’s Law of GravitationNewton’s Law of Gravitation• Newton’s law of gravitation states: Two bodies attract each other with a

force that is directly proportional the product of their masses and is inversely proportional to the square of the distance between them.

gmF

m

mkgkgNm

F

d

mGmF

grav

object

grav

grav

26

242

211

1038.6

1097.51067.6

2

21

g ~ 10 m/s2 “the acceleration of gravity”

And g x m is your weight!!

Newton’s Law and GravitationNewton’s Law and Gravitation• All my favorite Projectiles behave like this!!!

Force

Velocity

Acceleration

Newton’s Laws and Kepler's Newton’s Laws and Kepler's LawsLaws

• Newton’s law of gravitation and his three laws of motion prove all of Kepler’s laws

Newton's friend Edmund Halley predicted the comet would return in 1758 and it did!

Lecture Tutorial -- pg. 29 Lecture Tutorial -- pg. 29 Gravity and Newton's LawsGravity and Newton's Laws

• Work with a partner!• Read the instructions and questions carefully.• Discuss the concepts and your answers with one

another.• Come to a consensus answer you both agree on.• If you get stuck or are not sure of your answer, ask

another group.• 10 MINUTES

Newton’s Law of GravitationNewton’s Law of Gravitation• To figure out the gravitational force just

multiply the mass of the two things together then divide by the distance they are apart (squared).

2

21

d

mGmFgrav

m1

m2

d

Exam 1Exam 1

•Exam 1 statistics:

•N = 86/89

•Average = 57.2

•Median = 61

•Mode = 70

•Stddev = 18.8

•High = 88

•Low = 29