AP® Physics: The Scaffolded Block Scenarios
In AP® Physics this year, I did something different when introducing Newton's Second Law and drawing free body diagrams (FBDs). Typically, I would give the students a variety of scenarios to examine. This time, I decided to take two critical scenarios for a block and examine every possible presentation.
Below, I have included what this investigation looked like in my forces packet. Side note: I provide a packet at the start of each unit that students must bring to class. The packet includes a section for notes, guided discussions, simple investigations, and problems.
Block on a Ramp
- were introduced to symbolic analysis of problems as they are used to numerical answers at this early point in the year.
- realized that "at rest" and "at rest while on the verge of slipping" are different, even though the block is behaving the exact same way!
- discovered at rest and moving at constant velocity are nearly the same (both balanced)! The friction simply shifts from static to kinetic.
- determined the component of gravity responsible causing the block's acceleration and that, like in free fall, the mass of the block doesn't contribute to acceleration.
Stack of Blocks
- reaffirmed the conditions for static and kinetic friction from the previous investigation.
- found out they could look at a system of individual boxes or the boxes together! This was really good for them to see and emphasized the importance of Newton's 3rd law.
- discovered that, when the blocks had two different accelerations, they could not be combined into one system for second law (conditions 5 and 6)!
- analyzed how the direction of friction changes with the direction of acceleration.
Where do I want to go from here?
I am adding this to my list of summer goals!