Phy122_0902 - Physics 122 September 2, 2010 Question #1:...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
Physics 122 September 2, 2010 Question #1: Are you registered OK? With all the course info I gave you yesterday, I forgot i hts f th diff r nt p rts Th r in th the weights of the different parts. They are in the syllabus: Homework 15% Clickers 10% Labs 25% idterms % each Midterms 15% each Final 20% he Help Room has been moved to Physics A 1 The Help Room has been moved to Physics A-131. Shared with Physics 121.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
You log in to WebAssign for this course via Blackboard. Alternate route: Uses Shibboleth to validate your netid assword and direct you to WebAssign. password and direct you to WebAssign. http://webassign.net/sunysb/login.html I do not know how to set a password so that you can log into WebAssign for this course directly. Try the WebAssign tech support line.
Background image of page 2
At the end of last class, I asked the following clicker uestion but we did not have enough time for you to work F? question, but we did not have enough time for you to work on it. Charges of +1 μ C are placed as 10 cm shown at the four corners of a square, 10 cm on a side. What is the net force on the charge at the upper right? +1 μ C 10 cm With the hint that you lready know the solution +1 μ C already know the solution to this problem is 1.27 N
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
4 ea. Without the hint: 10 cm +1 μ C Each red arrow represents a force of magnitude x10 9 (1x10 -6 2 (0.1) 2 = 0.9 N 9x10 x(1x10 ) /(0.1) 0.9 N The solid blue arrow represents force of magnitude a force of magnitude 9x10 9 x(1x10 -6 ) 2 /(0.141) 2 = 0.45 N which has components F x = 0.45 N cos45 ° = 0.318 N F y = 0.45 N cos45 ° = 0.318 N Net force has components F x = 0.900 + 0.318 = 1.218 N F = 0.900 + 0.318 = 1.218 N F y . 9 .8 N F = (1.218 2 + 1.218 2 ) ½ = 1.72 N, up and to the right.
Background image of page 4
F? 10 cm Using the hint: We already know that the force due to the upper left and lower ght charges is 1 27 N directed to +1 right charges is 1.27 N, directed to the upper right. 1 μ C Adding the lower left charge is an additional force 62 ( 11 0 ) 10 0 45 N t n in th s m di ti n × 9 2 91 0 0 .45 Newton, in the same direction (2 0 . 1 ) ×= × Since these two forces are in the same direction, we can just add them as numbers, and the net force is 1.27 + 0.45 = 1.72 N, up and to the right.
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Presence of the charges causes something in their g neighborhood, even if there is no charge to feel a force. Whatever charge I put, there will be a proportional force. Force 1.72 N n 1 Force = 72x10 /C) x q 10 cm 10 cm on 1 μ C (1.72x10 6 N/C) x q q +1 μ C +1 μ C
Background image of page 6
Notation – vectors are denoted by bold face or Concept: Electric Field “The electric field E produced by a charge Q at the y arrow over the top. f py g Q location of a small “test” charge q 0 is defined as the electric force F exerted by Q on q divided by the test harge hat’s a lot of words charge q . That s a lot of words. Coulomb: Force between two charges acts at a istance distance. Faraday: Charge Q creates an electric field throughout space, and any charge q that is put in a q field feels a force = q E.
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 8
This is the end of the preview. Sign up to access the rest of the document.

This document was uploaded on 10/18/2010.

Page1 / 42

Phy122_0902 - Physics 122 September 2, 2010 Question #1:...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online