Friction Lab

## WHAT IS IT?

The model demonstrates how static friction and kinetic friction govern the transition between rest and motion. It lets you explore how the applied force (or angle of incline), mass, and friction coefficients determine whether the book stays still, starts moving, accelerates, or slows down.

## HOW IT WORKS

This model is a bunch of repeated applicaitons of newtons second law. When the book is at rest, static friction resists motion up to a maximum value. If the applied force (or the downslope component of gravity) is smaller than this, the book stays still. Once motion begins, static friction is replaced by kinetic friction. The book then accelerates or decelerates according to the net force direction.

## HOW TO USE IT

To replicate our lab, set μstatic to 0.577, and μkinetic to 2.25. For our pulling force, we measured about 2.25N (use the monitor to get the right slider value) and the book fell at around ~30°. 

Other then that, much can be learned when you mess around with the doodads provided. **Only one lab can run at a time, you must stop the current button, and re-setup.**

setup: Initializes the world and creates the book on the surface.

go (μk): Runs the simulation on the tilted table

go (μs):  Runs a version that checks whether static friction prevents motion. (ground)

freeze – book is held in place

pen? – When ON, the book leaves a trail of its motion on the floor.

table-angle-or-pull-force: The main input.

* In angle mode, it represents the incline angle (°).

* In force mode, it represents a horizontal pulling force (in poundals)

g: Gravitational acceleration (default 9.8 m/s²).

μ-static: Coefficient of static friction between the book and surface.

μ-kinetic: Coefficient of kinetic friction (forced smaller than μs).

the-book-mass: Mass of the book (in kilograms).

## THINGS TO TRY

- try to break it 

- try seeing exactly when things move

- etc.