Plan the investigation
What students will do
Use the student handout to organize predictions, measurements, and explanations.
- Predict the forces. Calculate the normal force and maximum static friction. Predict actual friction for a push below the threshold.
- Locate breakaway. Test applied forces and narrow the interval between the largest resting trial and the smallest sliding trial.
- Compare two states. Apply the same force first from rest and then with an initial velocity. Compare friction and subsequent motion.
- Change static friction. Predict and test how increasing only the static coefficient affects breakaway and friction during sliding.
What students will learn
- Distinguish actual static friction from its maximum value.
- Report a measured transition as an interval.
- Choose the appropriate friction model for the object’s state.
Common misconception
Is static friction always equal to its maximum value?
Before sliding, static friction adjusts to the required force balance up to its limiting value.