Math as Problem-SolvingMath as Problem-Solving

Active Physics asks students to problem-solve

Some of this problem-solving involves math

Some of the math is encoded in the language of word problems.

What do you do when you don’t know what to do?

rereading the problem using what you already know looking for patterns applying the solution to a similar problem making a picture of diagram

Word Problem Context

Home Module, Student Text, page 56. Power = current x voltage P = IV

Issues for the Uninitiated

Need for units• “I’ll take 100?”• one hundred of what?

Units and variables• P power in Watts (W)• I current in Amperes (A)• V voltage in Volts (V)

The Word Problem

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.

What are some issues that this problem raises for the uninitiated?

What’s the problem?

What’s unknown? What is given? What mathematical relationship do I use?

Solution: Substitution

P = I V 60W = A? 120V What number when multiplied by 120 gives

60?

Solution: Rearrangement

P = I V Divide both sides by V

P / V = I V / V The result is

I = P / V Now substituting

? = 60 W / 120 V

VIVVP // VIVVP //