# Week Fourteen – Rotational Motion & Simple Harmonic Motion

In Class Activity Plan

25 min – Whiteboard – Satellite Centripetal Ranking Problem (Word, Pdf)

PURPOSE: Practice modeling centripetal acceleration situation.
Lots of options here probably want to give one as homework:

20 min – Board Meeting

PURPOSE: Build consensus around modeling centripetal acceleration situation.

Goals:

• Centripetal force is just the net force towards the center
• Need to attend to the radius of the circular path

Additional resources which could be used:
Ferris Wheel Centripetal Force (Word, Pdf)
Centripetal Force Ranking (Word, Pdf)
Circular Motion Problems (Word, Pdf)

20 min – Whiteboard – Ladybug revolution part 1

PURPOSE: Investigate rotational motion, introduce rotational analogs to translational kinematics

Give students 10 minutes to explore.
Summarize what you have learned on whiteboard.

10 min – Board Meeting

PURPOSE: Share what was learned from investigation of simulation

20 min – Whiteboard – Ladybug Revolution part 2

PURPOSE: Develop models for constant rotational motion from graphs of rotational motion.

Use the second tab which shows graphs, use radians.

Answer: What have you learned? What rules can you make? What questions do you have?  On whiteboard.

20 min – Board Meeting

PURPOSE: Reach consensus about equations that describe constant angular acceleration motion.

1. Review the kinematic representations in the basic 1-d constant acceleration model

a) Equations

d = Δpos
v = Δpos/Δt
a = Δv/Δt
d = v0 + ½at2
vf = v0 + at

b) Velocity-time graph 1. When does this model apply?

Answer: when we have straight line motion

1. What is the motion of the wheel?

Answer: not moving linearly, but it is movingt

1. Create a table of angular variables by analogy
 d = Δpos θ = Δangle v = Δpos/Δt ω = Δangle/Δt a = Δv/Δt α = Δω/Δt d = v0 + ½at2 θ = ωt + ½ α t vf = v0 + at ωf = ω0 + at

1. How should be able to go between the two versions?

a) d = r θ
b) v = r ω
c) a = r α

1.  Now we can add on the rest of relationships
 m I = åmiri p = mv L = Iω Fnet = m a t = Iα Eklinear = ½ m v2 Ekrot = ½ I ω2

25 min – Whiteboard- Helicopter Quantitative Problem (Word, Pdf)

PURPOSE: Model situation with constant angular acceleration

20 min – Board Meeting

PURPOSE: Build consensus about modeling constant angular acceleration

Homework – Ranking of Theta vs t graph (Word, Pdf) and Rotational speed ranking (Word, Pdf)