1. Math as Problem-Solving w Active Physics asks students to problem-solve w Some of this problem-solving involves math w Some of the math is encoded in the language of word problems.

2. What do you do when you don’t know what to do? w rereading the problem w using what you already know w looking for patterns w applying the solution to a similar problem w making a picture of diagram

3. Word Problem Context w Home Module, Student Text, page 56. w Power = current x voltage w P = IV

4. Issues for the Uninitiated w Need for units “I’ll take 100?” one hundred of what? w Units and variables P power in Watts (W) I current in Amperes (A) V voltage in Volts (V)

5. The Word Problem w How much current, in amps, must be flowing through the filament of a 60-W light bulb when it is operating in a 120-V household circuit? A 100- W light bulb? Show your calculations in your log. w What are some issues that this problem raises for the uninitiated?

6. What’s the problem? w What’s unknown? w What is given? w What mathematical relationship do I use?

7. Solution: Substitution w P = I V w 60W = A? 120V w What number when multiplied by 120 gives 60?

8. Solution: Rearrangement w P = I V w Divide both sides by V P / V = I V / V w The result is I = P / V w Now substituting ? = 60 W / 120 V