Week 9 121 W2020

Before Class

  • Please finish PS#8 in fine form.
  • Send me a description of your planned project #2
  • Finish your project #1 to hand in by tomorrow, Tuesday.
  • See this video about the mass on the inclined plane (9.5 minutes)
  • Read 7.2
  • A video on the conical pendulum
  • Read 7.3 on the conical pendulum. 
  • On Tuesday, I will have an extra office hour after class (the after-party party), instead of an office hour after class on Thursday

During Class
Estimate normal force or tension, acceleration


Before Class

During Class 

  • Practice slack lining?

This week, we review a little and also study the final topic: How torque is the rate of change of angular momentum, and how they are both vectors, so when torque is perpendicular to angular momentum, torque doesn’t increase or decrease angular momentum. Instead, torque causes the angular momentum to change direction. This is precession.


Before Class

  • Please see solutions to PS#8, posted on main class website.
  • see video Veritassium Which Block Goes Higher?
  • See video on Inclined Plane using Only Energy (no kinematics at all!) (3.5 minutes)
  • Read 7.6 on equations and trigonometry that you are now allowed to use.
  • See Trigonometry Video , now you’re allowed to use trigonometry, but remember you can also draw a picture and estimate instead. Additionally a drawing will help if you’re not sure of the trig solution.
  • See 1D, 2D Kinematics Video illustrating the use of these equations,. Please be aware that you can continue to solve these problems just fine without these equations.
  • Please take this short Survey #4
  • Project #2 due by midnight this Saturday, March 7.

During Class

  • Assessment on components
  • Why must we spin frisbees or footballs to make them fly stable?
  • Precession – what is it?

Thursday: We look at angular momentum as stability.

Before Class

In Class

  • What is precession?

After Class

Post Video Project by midnight Saturday night.