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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 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?
academicearth.org Lecture 69 introduction-to-newtons-law-of-gravitation • 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