Monday, October 15, 2001

• Exam 2 is now scheduled for Friday, October 26
• Next Tuesday, Oct. 23:  Talk about the Nobel prize in physics instead of office hour
• 12:30 in Phillips 277:  "Bose-Einstein condensates"
• Group Web Projects topics are due by 5:00 pm today.

Torque = Force x Lever Arm

Moment of inertia depends on the mass of an object and where that mass is distributed relative to the axis of rotation.

Rotational analog of F = ma:  Torque = (moment of inertia)(angular acceleration)

Conditions for equilibrium:
1)  Net external force is zero
2)  Net external torque is zero

Rotational kinetic energy:  KEr = 0.5*Iw²

Angular momentum:  L = Iw

Angular momentum is constant if there is no net torque on a rotating object.
    Torque = dL/dt

Ponderables:

1. Which gives more torque when turning a screw:  a long or short screwdriver?
2. Why is it easier to turn a small screw into wood, but a large screw is difficult?

• Which object will fall over?
• How can you apply the maximum torque to a nut?
• If a meter stick balances at the 25 cm mark when a 1 kg mass is hung from the 0 cm end, what is the mass of the meter stick?

• center of mass of NC
• balancing bird and wine bottle
• inertia rods
• teeter totter

• HW8b (due Monday, Oct. 22)
• RWP8 - Stilt Walker (due Monday, Oct. 22)
• Original RWP for Exam 2