Physics121C_L21 - Physics 121C Mechanics Lecture 21...

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
Physics 121C - Mechanics Lecture 21 One-Dimensional Rotation November 24, 2004 John G. Cramer Professor of Physics B451 PAB [email protected]
Background image of page 1

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

View Full DocumentRight Arrow Icon
November 24, 2004 Physics 121C - Lecture 21 2 Announcements Homework Assignment #6 has been posted on Tycho and is due tonight, Wednesday, November 24 at 9:00 PM. The last question of the last problem (“Space Explorer”) of Homework Assignment #6 on Tycho does not make sense. It will not be counted. Do not attempt it. However, be sure to answer the first three questions of the problem.
Background image of page 2
November 24, 2004 Physics 121C - Lecture 21 3 8 15-Nov-04 17 Work 11.1 to 11.5 Work and Energy Angular Acceleration 17-Nov-04 18 Energy Conservation 11.6 to 11.9 19-Nov-04 19 Universal Gravitation 12.1 to 12.5 9 22-Nov-04 20 Orbits & Rotation No Tutorials Make-up Labs 24-Nov-04 21 1-D Rotation 26-Nov-04 HOLIDAY - 10 29-Nov-04 22 Energy & Angular Mom. 13.7-13.10 Angular Momentum Simple Harmonic Motion 01-Dec-04 R3 Review & Extension - 03-Dec-04 EXAMINATION 3 - Chapters 11-13 Lecture Schedule (Part 3) You are here!
Background image of page 3

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

View Full DocumentRight Arrow Icon
November 24, 2004 Physics 121C - Lecture 21 4 Plotting α and ϖ The angular acceleration α is the rate of change of the angular velocity ϖ . If the angular acceleration α and the angular velocity ϖ are plotted vs. time t , then α is the slope of the ϖ vs. t curve, and ∆ ϖ = ϖ ( t f 29-ϖ (t i ) is the area under the α vs. t curve in the time interval between t i and t f . d dt ϖ α= f i t t dt α =
Background image of page 4
November 24, 2004 Physics 121C - Lecture 21 5 Example : A Rotating Wheel Figure (a) shows the angular velocity ϖ vs. time t. What rotational behavior does it describe, and what is the angular acceleration α ? The angular velocity ϖ is positive, so the plot describes a counterclockwise rotation that increases from t=0 to t 1 , remains constant from t=t 1 to t 2 , and decreases to a halt from t=t 2 3 . Figure (b) shows the corresponding angular acceleration α .
Background image of page 5

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

View Full DocumentRight Arrow Icon
November 24, 2004 Physics 121C - Lecture 21 6 Rotational and Linear Kinematics α is constant a is constant
Background image of page 6
November 24, 2004 Physics 121C - Lecture 21 7 Example : A Rotating Crankshaft A car’s tachometer indicates the angular velocity ϖ of the crank shaft in rpm. A car stopped at a traffic light has its engine idling at 500 rpm. When the light turns green, the crankshaft’s angular velocity speeds up at a constant rate to 2500 rpm in a time interval of 3.0 s. How many revolutions does the crankshaft make in this time interval? 500 rpm (2 rad/rev)/(60 s/min)=52.4 rad/s i ϖ π = × 2500 rpm 5 262.0 rad/s f i = = = 2 (262.0 rad/s 52.4 rad/s) 69.9 rad/s (3.0 s) f i t α - - = = = ( 29 ( 29 2 1 2 2 1 2 2 0 (52.4 rad/s)(3.0 s) (69.9 rad/s ) 3.0 s 472 rad 75 rev f i i t t θ = + ∆ + = + + = =
Background image of page 7

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

View Full DocumentRight Arrow Icon
November 24, 2004 Physics 121C - Lecture 21 8 Clicker Question 1 The fan blade shown is slowing down. Which option describes α and ϖ ?
Background image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/29/2009 for the course PHYSIC 1D03 taught by Professor Dr.reid during the Spring '09 term at McMaster University.

Page1 / 34

Physics121C_L21 - Physics 121C Mechanics Lecture 21...

This preview shows document pages 1 - 9. Sign up to view the full document.

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