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Solving Forces Problems (Brain Dump)

October 1, 2017

Next few weeks in first semester physics we start  solving forces problem.

I’m doing this in a couple stages:

  • 1D Horizontal dynamics: 
  • 1D Vertical dynamics and weight 
  • Friction
  • Static Equilibrium in 2D
  • Dynamics in 2D
  • Interacting Objects

Here are some details about what we are doing this week. 

The horizontal dynamics starts by building off our half Atwood’s experiments, by introducing a second pulley that pulls back on the cart. 


This introduces us to the idea of net force and representing forces using FBDs. We do some card sort ranking tasks (rank Fnet and rank by acceleration) and clicker questions with FBDs. 

Students end up solving three problem types: unknown acceleration, unknown mass, unknown force. I’m doing so, We also cycle back to review kinematics, since our forces Problems with unknown acceleration involve finding a final speed and position. Students are expected to make graphs and equations that represent motion. 
The vertical dynamics begins with gravitational force lab, to introduce model  concerning 10 N/kg. Using demos and clicker questions, we talk about how to properly and improperly use scales (if you want measure your true weight), and build up idea of apparent weight as normal force. We do some card sorting activity of situations where normal force would be larger than, less than, equal to, or not enough information to decide.


The day ends representing and then solving elevator ride problems. We actually get on elevator with vernier scale, and use that data to determine mass or rider, top speed, and total distance traveled. 

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