Semester 2 – Day 5


Today students did a simple lab to calculate the coefficient of kinetic friction from a plot of experimentally measured kinetic friction force vs. normal force.

To introduce the lab, I gave them a follow up quiz to the weight-mass lab last week, that has them calculate the various forces on an object being dragged at constant velocity along a surface.

Here is where I still see confusion in my students
• Weight and mass are still identical in their minds
• Weight and the Force of gravity from Earth on an object are considered to be related but distinct ideas (they are in fact identical ideas on the surface of the Earth)
• The gravitational strength g, is a unit conversion that helps them convert units from weight in kg to weight in N

I have no idea how to alter this idea in their heads without taking them to the moon.


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