Oscillations Monday, November 19 Lecture 30

Workbook problems due Wednesday WB 10.5, problems 14-25

Workbook Problems due Friday Problems 14-1 through 8, pages

Power Power is the rate of transformation of energy Unit is 1 Watt=1W = 1 J/s If energy being transformed is work, W then

Is the work done by F + or - ? 1.Positive 2.negative F d

Is the work done by F + or - ? 1.Positive 2.negative F d

Is the work done by F + or - ? 1.Positive 2.negative F d

Problem 10:20 A pendulum is made by tying a 500g ball to a 75-cm-long string. The pendulum is pulled 30 0 to one side and then released. A) What is the ball’s speed at the lowest point in its trajectory? B) To what angle does the pendulum swing on the other side.

Problem 10:20 Use energy conservation 30 0 L=0.75 m Δy=L-Lcos 30 0

Problem 10:20 cont Set y=0 at lowest point of swing

Problem 10:24 A student places her 500g physics textbook on a frictionless table. She pushes the book against a spring 4.00cm and then releases the book. What is the book’s speed as it slides away? The spring constant is k = 1250 N/m.

Problem 10:24 A student places her 500g physics textbook on a frictionless table. She pushes the book against a spring 4.00cm and then releases the book. What is the book’s speed as it slides away? The spring constant is k = 1250 N/m.

Problem 10:24 Using the initial position as the compressed spring, final after book leaves spring:

Problem 10:24 Finally

Equilibrium and Oscillation Frequency and Period

Simple Harmonic Motion Linear restoring force— – Example, mass on a spring – Set y=0 at equilibrium point: –

Simple Harmonic Motion If restoring force is linearly proportional to displacement (e.g. F=-kx) then we will have simple harmonic motion. In lab last week you experimented with a simple pendulum. Was its motion simple harmonic?

θ w cos θ w w sin θ T

Simple Pendulum Find the angular frequency is

Description of motion

a)At what time(s) is particle moving right at maximum speed? b)At what time(s) is particle moving right at maximum speed? c)At what time(s) is the speed zero?

Problem 14:7 An air-track glider is attached to a spring. The glider is pulled to the right and released from rest at t=0s. It then oscillates with T=2.0s and v max = 40cm/s a)A=? b)x(t=0.25s) = ?

Problem 14.7

Wednesday Oscillations continued Problems CQ3,CQ9,MC18,MC19, 1, 4, 6, 7, 10