LESSON 8

PHYS 1100 LESSON 8 FOR
TUESDAY, AUGUST 17, 2010

I Introduction

II Logistics – Running Grades

III Turn in Assignments Due and Return of Papers

IV Review of Lesson 7: Energy, Momentum, Torque, et al
Energy: interchangeable with mass, per

Einstein’s E = mc2.

41H1 = 2He4 + mc2 + 2b+.

F d = using energy = Joules. Work is useful energy. Efficiency, e = W/E, e<1

Natural gas: CH4 + 2O2 = CO2 + 2H2O + Energy


Gasoline: 2C8H18 + 25O2 =
16CO2 + 18H2O + Energy

Momentum, p = m v goes in a straight line

Angular momentum, l = m v r

V Lesson 8: Inertia, Torque, Gravity

A. Inertia is kg m2.
B. Torque is N-m
C. Gravity:

1. Kepler – P2 (m + M) = [(4 p2)/G] r3.

This is Kepler’s 3rd law dealing with the period of a planet, P, with a mass, m, traveling around the Sun, with a mass, M, at a distance between the Sun and the planet equaling “r”. However, it applies to moons, asteroids, stars, satellites, blah blah.

Period is in seconds, mass in kilograms, distance in meters (mks). The Universal Gravitational Constant is G = 6.67 x 10-11 N m2 / kg2.

2. Newton – F = GmM/r2.

This part of Newton’s 2nd Law, which deals with the force, F, of gravity.

Little ‘m’ is the mass of a smaller object, such as human; big “M” is the mass of the larger object, such as planet Earth; r is the distance between the center of the first object (like a human’s navel) and the center of the second object (like the distance from the human to Earth’s core, i.e., the radius of Earth.

As a force, instead of a period, this law applies both to moving objects, like planets, moons, stars; and to object that are not moving, like people standing on Earth, or between two bowling balls in a bowling alley.


The Universal Gravitational Constant is G = 6.67 x 10-11 N m2 / kg2.

VI Laboratory Exercise 8: Simple Harmonic Motion


VII HWK Assignment 3: 10-14 and do Problems 1, 3, 9, 13, 19, 25, 29, 31, 39, 53, 63, and 65 on pp 323-327; Problems 1, 3, 9, 13, 19, 25, 29, 31, 39, 53, 63, 65 and 77 on pp 366-371; Problems 1, 3, 9, 13, 19, 25, 29, 31, 39, 53 and 63 on pp 409-412; Problems 1, 3, 9, 13, 19, 25, 29, 31, 39, 53, 63, and 65 on pp 445-448; and Problems 1, 3, 9, 13, 19, 25, 29, 31, 39, 53, 63, 67, 69, and 77 on pp 491-495; due 8/19

VIII Essay 3: James Prescott Joule, due 8/19