Simple harmonic motion is quite common and describes the motion of an object when it's displacement causes a restoring force F = -kx.  The motion of a mass on a spring or a swinging pendulum are typical examples.

			This means the amplitude of oscillation follows a sine or a cosine curve with constant period.

			Even as the amplitude decays due to air resistance or friction, the period remains constant.

			Simple harmonic motion is described by the equation: where A is the amplitude of the motion, T is the period (seconds per cycle), f (= 1/T) is the linear frequency (cycles per second) and ω is the angular frequency (radians per second).

			The graph below shows simple harmonic motion as a function of time with an amplitude of 5, a frequency of 2 cycles per second, a period of 0.5 seconds per cycle, and an angular velocity of 4π radians per second:

			As a point moves at a constant speed around a circle, its projection (shadow) onto the y-axis traces out a sine curve.

			As a point moves at a constant speed around a circle, its projection (shadow) onto the x-axis traces out a cosine curve.

			Read pp. 348-362 and 366-368 of the text.

			Answer the questions in HW 19 on WebAssign:  http://webassign.net/login.html