# Day 57: Balanced Force Lab Practical

College-Prep Physics: Today we did a balanced force lab practical to tie together all our work on forces. It’s similar to the ones I’ve written about in past years. However, this year we used the green buggies and whiteboards instead of wood blocks and carpet/rubber. (This is because this year, in previous labs, some groups already worked with wood blocks and carpet/rubber.)

Given only a green buggy, a whiteboard, a spring, a 200-gram mass, and a ruler:

1. Determine the spring constant of your spring.
2. Determine the weight of your green buggy.
3. Determine the force of kinetic friction between your buggy’s rubber tires and your whiteboard.
4. Determine the coefficient of kinetic friction between your buggy’s rubber tires and your whiteboard.
5. Predict the force of kinetic friction when 500 grams is added to your buggy. Have your teacher test your prediction!

UPDATE 2014 DEC 3: We found that when the 500 gram mass is added to buggy, the buggy rolls (rather than slide) when pulled. A binder clip on a rear wheel works great to lock the wheels so the buggy slides.

NGSS Science and Engineering Practices:
#2. Developing and using models
#3. Planning and carrying out investigations
#4. Analyzing and interpreting data
#5. Using mathematics and computational thinking

##BFPM