Transcript Math as Problem

Math as Problem-Solving
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Active Physics asks students to
problem-solve
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Some of this problem-solving involves math
Some of the math is encoded in the
language of word problems.
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What do you do when you
don’t know what to do?
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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
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Home Module, Student Text, page 56.
Power = current x voltage
P = IV
Issues for the Uninitiated
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Need for units
• “I’ll take 100?”
• one hundred of what?
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Units and variables
• P
• I
• V
power in Watts
current in Amperes
voltage in Volts
(W)
(A)
(V)
The Word Problem
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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 100W light bulb? Show your calculations in your log.
 What are some issues that this problem raises for
the uninitiated?
What’s the problem?
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What’s unknown?
What is given?
What mathematical relationship do I use?
Solution: Substitution
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P = I V
60W = A? 120V
What number when multiplied by 120 gives
60?
Solution: Rearrangement
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P = IV
Divide both sides by V
P/V = IV/V
The result is
I = P/V
Now substituting
P / V  IV / V
P / V  IV / V
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? = 60 W / 120 V