A 2 kg sample of air contained in a 2 m3 rigid container undergoes a process in which its pressure reduces from 100.45 kPa to 86
.10 kPa while the volume remains the same. Please calculate (a) how much work was done, (b) by how much did the internal energy of the air change, (c) how much heat was transferred (please specify the direction of heat transfer).
1 answer:
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When the person is in the elevator, the scale says 77 kg. The scale is still using the same value of conversion (9.81), so the apparent weight "felt" by the scale is
This is the normal reaction applied by the scale on the person, and which is directed upward. Besides this force, there is still the weight W of the person, acting downward. So, if we use Newton's second law:
where a is the acceleration of the elevator. If we solve for a, we find
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Answer: R = 394.36ohm
Explanation: In a LR circuit, voltage for a resistor in function of time is given by:
ε is emf
L is indutance of inductor
R is resistance of resistor
After 4s, emf = 0.8*19, so:
R = 394.36
In this LR circuit, the resistance of the resistor is 394.36ohms.