LESSON 7

PHYS 1100 LESSON 7 FOR
MONDAY, AUGUST 16, 2010

I Introduction

II Logistics – Running Grades

III Turn in Assignments Due and Return of Papers

IV Review of Lesson 6: Energy, Work, Momentum, Angular Momentum, Impulse

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 7: Torque, Inertia, Impulse

Impulse = I = F Dt. Baseball, golf, billiards, tennis. N-s units of Impulse

F = m a

I = (ma) Dt = m(a Dt) = m (Dv/Dt)(Dt) = m(Dv)( Dt/Dt) = mDv = p

Example: What force does a baseball hitter use when he hits a 0.15 kg ball, traveling at 160 km/hour, and the contact time, Dt = 0.12 sec?

m v = F Dt

So, WTF?

(m)(v)/(dt) = F = (0.15)(44.5)/(0.12) = 55.625 N

160 km/hr = (5/18)(160 km/h) m/s 44.5 m/s

55.625 N = 56 N ~ 5.6 E1 or x 10^1 or 101 N.

Torque has the name units as Energy; torque, t, = r F; N-m

Inertia = characteristic of matter that resists change units are kg m2.

VI Laboratory Exercise 7: PE KE


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