GRAVITY For two particles that have masses m 1 and m 2 and are

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GRAVITY For two particles that have masses m 1 and m 2 and are separated by a distance r , the force has a magnitude given by. 12.0 Kg. 25.0 Kg. 1.20 m. What is the Initial Force between m 1 and m 2 ?. academicearth.org Lecture 69 introduction-to- newtons -law-of-gravitation.

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## GRAVITY For two particles that have masses m 1 and m 2 and are

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GRAVITY

For two particles that have masses m1 and m2and are

separated by a distance r, the force has a magnitude given by

12.0 Kg

25.0 Kg

1.20 m

What is the Initial Force between m1 and m2?

• F gravity = (G * M 1 * M 2)/ (d2)
• G is 6.67 X10 -11 Nm2 / kg2
• F gravity = (m * “g”) = (mass times gravitational acceleration) =Weight
• DO NOW: What is the Force of attraction between “P” and “A” if “P” has a mass of 50.0 Kg and “A” has a mass of 65.0 Kg and they are separated by 1.00 meter? __________N
• If “Purple” is held stationary and “Austin” is allowed to move n a totally frictionless surface (NO other forces!) from rest AND if the INITIAL Acceleration remains constant…HOW LONG will it take “A” to “contact” “P”? _________Sec

m1 = 50.0 Kg

m2 = 65.0 Kg

r = 1.00 m

F = [6.67X10-11 (50.0 *65.0)] /1m2

ANSWEWR Part ONE F = 2.17 X10-7 N

m2 a = F = 2.167 X10-7 N

a = F/m2 =2.167 X10-7 N /65.0 = 3.335 X10-9 m/s2

D = Vi(t) + ½ a t2

1.00 m = 0 + [½] {3.335 X10-9 m/s2} t2

5.997 X108 s2 =t2

2.448877 X10 4 sec = 2.45 X10 4 sec

408 minutes = 6.8 hrs

Gravity Homework: Glencoe Pages 191-192 43,45,46, 49, 58,59,62,71,72
• discovery.com stephen-hawkings-universe-cosmic-gravity-dance.html
Definition of Weight

The weight of an object on or above the earth is the gravitational force that the earth exerts on the object.

Weight is written as m * g

F grav= Weight = Mobj*g

F grav= {G MobjMEarth }/ (Radius)2

Mobj*g = {G MobjMEarth }/ (Radius)2

g = {G MEarth }/ (Radius)2

g = {6.67X10-11 5.9624 X 1024 }/ (6.37814 X 10 6)2

g = 9.77595 m/s2

What is keeping the moon from “falling” into the Earth?

Mass of the Earth : 5.9624 X 1024 Kg

Mass of the Moon:7.2997 X 1022 Kg

Orbital distance from the Moon to Earth :0.3844 X106 Km

Orbits Centripetal Force

Homework: Glencoe Pgs 191-192: #’s 43,45,46, 49, 58,59,62,71,72

Pgs : 195 ‘s 1 – 6 ALL

Homework: Serway Pgs 451#’s 9, 12,14, 18, 19

• F centripetal = M obj{V2/ R }
• (R and d are sometimes used interchangeably when talking about orbits)
• Gravity = (G * M obj * M planet)/ (d2)
• Orbits are in “Balance”
• M obj V2 / R = (G * M obj * M planet)/ (d2)
• V2 / d = (G * M planet)/ (d2)
• V2 = (G * M planet)/ (d)
• V =√[ (G * M planet)/ (d)]
Next Class Kepler’s Third Law

(T “A” / T “B”)2 = (R “A” / R “B”)3

(Period of Orbiting Object “A” / Period of Orbiting Object “B”)2

=

(Radius of Orbit for Object “A” / Radius of Orbit for Object “B”)3

“B”

“A”

{TA/TB}2 = {RA / RB}3