In Physics 11 the concept of torque is often quite easy to calculate but, from my experience, is not something that many students fully understand. The implications of torque are enormous in engineering but also have real world applications for our students. Many of our students have been on a ‘teeter-totter’ and experienced the effects of leaning back to go down faster. I would present students with the problem of a loaded bench press (4-45lbs plates a side) and ask their thoughts on how many plates I can take off one side before the bar flips. The intention of using this example is it would relate to my students and would have them think about torque in their daily lives.
I would use the following question to guide the inquiry process:
How can we explain the gym using physics? What is the safest design of a bench press to prevent weight tipping?
The question is intentionally broad as there is no single answer to it. We will approach it through the lens of torque (and can revisit from other angles as we see fit – pulleys etc).
|Phase of Instruction
|Show students a picture of a loaded bar with 405lbs and ask how many 45lbs plates can be removed from one side before the bar flips. This is a complex question as the pivot point is very close to the heavier side. Ask students what they think will happen if a smaller bench press is used and the anchor points are closer together (the pivot point would be further from the weight).
|Students hypothesize what is going to happen, explore bench press design, design a bench press to minimize weight tipping yet is still usable and compare their results with others in the class.
|Evaluate the relationship
|Take the class to the weight room and recreate the situation and see what happens (teacher led – be careful!)
Have students complete the PhET simluation (https://phet.colorado.edu/en/simulation/balancing-act) on tourque and balance.
|Students test their theory with what actually happens and are given time to work with an unloaded bar (Safely!!) and see how position and pivot point effect when the bar will tip. Students capture their experiment using their devices and explain their findings in a video journal.
|Modify the relationship
|Other implications and extensions of where these theories of physics apply are covered (structural engineering, mechanical engineering)
|Students modify the design of their own bench press with detailed explanations of their design choice and answer the driving question.
Any thoughts or suggestions on the design process or the guiding questions?
Khan, S. (2007). Model-based inquiries in chemistry. Science Education, 91(6), 877-905.
Khan, S. (2010). New pedagogies for teaching with computer simulations. Journal of Science Education and Technology, 20(3), 215-232.