Rotation 01

OPENING QUESTIONS: Work with your crew to (as quick as you can) write down our formulae for rotational motion from a few weeks back

OBJECTIVE: I will be able to list the equations of motion for a rigid object under constant angular acceleration after today's class.

WORDS FOR TODAY:

Remember this?

FORMULAE & TERMS:

There are a veritable FLOOD of new terms to get comfortable with in this unit... so let's start NOW:

Term	Symbol	Formula	SI units	Description	Notes
radian	θ		radians	π (in radians) = 180^o	1 radian = 57.3 degrees
period	T		seconds	the period = time for one full rotation
angular speed	ω	∆θ/dt	radians/sec	∆θ/dt is instantaneous speed	angles ALWAYS described in radians
angular acceleration	α	dω/dt		dω/dt is instantaneous acc
tangential velocity		v_t = rω	m/s	linear velocity at any radial distance "r"
tangential acceleration	a_t	a_t = rω² rdω/dt	m/s/s
centripetal acceleration		a_c = v²/r or rω²	m/s²	acceleration of an object following a circular path	Be careful -- radians (by definition) are unitless
ω_f = ω_i+αt
θ_f=θ_i+ ω_i t+1/2 αt²
ω_f²=ω_i²+2α(∆θ)
θ_f=θ_i+1/2(θ_f+θ_i)

WORK O' THE DAY:

Take a few moments to review the terms and symbols above.

Now please copy down into your notes the four (count 'em 4!) equations of rotational motion. (They should look *rather* familiar in a different language sorta way).

Go through the worked examples: (10.1 begins on page 297 and 10.2 begins on 299)

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Page 325 (6, 10, 13 & 22) #22 is poorly written but it is kind of an interesting problem:

Picture a ladder that you've leaned up against your house. Unfortunately the ground is uneven so the ladder is twisted so that it won't lean up aginst the flat wall of your home correctly. In order to make it so both sides of the ladder are flush with the wall of your house you have to put a rock under the base of ONE side of the ladder. Try that..