Physics 121, Sections 9, 10, 11, and 12 Lecture 11 Today's Topics Homework 5: Due Friday Oct 7@6: 00PM Ch.5:#9,11,12,23,26,30,32,41,57,and63. Chapter 5: Rotation Angular variables Centripetal acceleration Kepler's laws Artificial gravity Physics 121: Lecture 11, Pg 1
Physics 121: Lecture 11, Pg 1 Physics 121, Sections 9, 10, 11, and 12 Lecture 11 Today’s Topics: Homework 5: Due Friday Oct. 7 @ 6:00PM Ch.5: # 9, 11, 12, 23, 26, 30, 32, 41, 57, and 63. Chapter 5: Rotation Angular variables Centripetal acceleration Kepler’s laws Artificial gravity
Chapter 5 Uniform circular Motion What does it mean How do we describe it What can we learn about it Physics 121: Lecture 11, Pg 2
Physics 121: Lecture 11, Pg 2 Chapter 5 Uniform Circular Motion What does it mean ? How do we describe it ? What can we learn about it ?
Recap: X=R COS(0)=R coS(ot) y=R sin(0)=R sin(ot) 0= tan1 (y/x) R S 0= ot =0t s=vt S=R0 Rot V=OR Physics 121: Lecture 11, Pg 3
Physics 121: Lecture 11, Pg 3 Recap: R v s =t (x,y) x = R cos() = R cos(t) y = R sin() = R sin(t) = tan-1 (y/x) = t s = v t s = R = Rt v = R
Centripetal Acceleration UCM results in acceleration Magnitude a=v2/R =02R since v= OR Direction ( toward center of circle) Physics 121: Lecture 11, Pg 4
Physics 121: Lecture 11, Pg 4 Centripetal Acceleration UCM results in acceleration: Magnitude: a = v2 / R = R since v = R Direction: - r (toward center of circle) R a ^
Problem: Rotating puck weight A mass m, slides in a circular path with speed v on a horizontal frictionless table it is held at a radius r by a string threaded through a frictionless hole at the center of the table. At the other end of the string hangs a second mass m2 What is the tension in the string T? What is the speed of the sliding mass v Physics 121: Lecture 11, Pg 5
Physics 121: Lecture 11, Pg 5 Problem: Rotating puck & weight. A mass m1 slides in a circular path with speed v on a horizontal frictionless table. It is held at a radius R by a string threaded through a frictionless hole at the center of the table. At the other end of the string hangs a second mass m2 . What is the tension in the string T ? What is the speed of the sliding mass v ? m1 m2 v R