A cube of iron (Cp = 0.450 J/g•°C) with a mass of 55.8 g is heated from 25.0°C to 49.0°C. How much heat is required for this pro
2 answers:
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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>
Answer:
Part a)
Part b)
Explanation:
Part a) what is its frequency, in rev/s
we have that
An old-fashioned LP record rotates at 33 1/3 RPM
so
Convert mixed number to an improper fraction
Remember that
Convert rev/min to rev/sec
Simplify
Part b) what is it period, in seconds
we know that
The period is the reciprocal of the frequency
therefore
the frequency is
<h3><u>Answer</u> :</h3>
Initial velocity = zero (i.e., free fall)
Final velocity = 30m/s
Acceleration due to gravity = 10m/s²
For a body falling freely under the action of gravity, g is taken positive
◈ <u>First equation of kinenatics</u> :
⇒ v = u + gt
⇒ 30 = 0 + 10t
⇒ t = 30/10
⇒ <u>t = 3s</u>
Hence, object will attain a speed of 30m/s after 3s.