# Gas station without pumps

## 2012 January 5

### Physics homework (Chapter 5)

Filed under: home school — gasstationwithoutpumps @ 22:59
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Chapter 5 in Matter and Interactions is the one in which they finally introduce the derivative of momentum, though they are very careful to say that $\vec{F}_{\mbox{net}} = d \vec{p}/dt$ is not an identity but a statement of causation: the net force causes the change in momentum.

I want to start discussing Chapter 5 tomorrow (2012 Jan 6) and have homework due next week 2012 Jan 13.  I’d also like to do a lab next week: perhaps estimating g from measurements of circular pendulum.  We should be able to set up a circular pendulum with a lego motor on one of the ceiling beams and have a nice long pendulum so that we can measure length of the string, radius of the circle, and period of the circle.  My son and I will work on building the Lego contraption so that we can get different speeds.  He also suggested that we use two weights (on equal length strings) so that we can keep the motor balanced. With any luck, the optical gate I ordered from Sparkfun should have arrived by then so that we can do very precise timing of the period.

Homework due Friday 2012 Jan 13:

5P14, 5P16, 5P19, 5P46, 5P52(this is the lab we’ll do together), 5P54, 5P56, 5P59, 5P65, 5P67.