A child has an ear canal that is 1.3 cm long. At what sound frequencies in the audible range will the child have increased heari
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Answer:
Uk = 9.9 J
Explanation:
To calculate the kinetic energie (Uk), you can make use of this formula:
Uk = 0.5 * m * v²
given m = 55 kg and v = 0.6 m/s
Substituting in the formula gives:
Uk = 0.5 * 55 * (0.6)²
Uk = 0.5 * 55 * 0.36
Uk = 9.9 J
Extra:
Now let's examine the formula in relation to the SI units. <em>If you understand the following, it will give you great insight in how smart Phisics is inter twained by looking at formulas and their standard units. It will save you time in future to convert formulas, if you use the right standard units.</em>
The formula for kinetic energie is:
Uk = 0.5 * m * v²
Standard SI unit for mass m is kg.
Standard SI unit for speed v is m/s.
So v * v = v² and therefore v² must have the standard SI unit of m²/s².
From the formula, you see that the unit of Uk must be kg*m²/s² and since Uk is normally given in J, these both forms must be the same !
The main unit for Uk is the Joule. <em>Now</em><em> </em><em>please</em><em> </em><em>see</em><em> </em><em>the</em><em> </em><em>picture</em><em>,</em><em> </em><em>which</em><em> </em><em>shows</em><em> </em><em>the </em><em>relation</em><em> </em><em>between </em><em>the </em><em>J </em><em>and </em><em>other</em><em> SI units</em><em>.</em><em> </em><em>Please</em><em> </em><em>understand</em><em> </em><em>that</em><em> </em><em>you</em><em> </em><em>can</em><em> </em><em>construct</em><em> </em><em>your</em><em> </em><em>'own'</em><em> </em><em>formulas</em><em> </em><em>based</em><em> </em><em>these</em><em> </em><em>units</em><em>.</em><em> </em><em>Now</em><em> </em><em>here</em><em> </em><em>is</em><em> </em><em>the</em><em> </em><em>time</em><em> </em><em>saver</em><em>:</em>
Because almost always the right units are <em>given</em> in a question, or because sometimes you can look up a constant in a table with an exotic and seemingly complicated unit, but that says a lot about the formula which must have been some how involved!
<em>By this, I hope you now understand the implication of using the right standard SI units and how that can help you figure out what formula is needed.</em>
