Question

The unit of power is:
A) $J{s^{ - 1}}$
B) $g{m^2}{s^{ - 3}}$
C) $kgc{m^2}{s^{ - 3}}$
D) $dyne{s^{ - 2}}$

Answer 1

Hint: Power is defined as the amount of energy transferred per unit time or work done per unit time. It is directly proportional to the amount of work done.Average power is the ratio of the total energy consumed and the time taken. Basically power gives us an idea of how fast or slow energy is getting transferred.


Complete step by step answer:
Step I:
The formula for power is written as
$P = \dfrac{{dW}}{{dt}}$
Where $P$ is the power
$dW$ is the amount of work done
$dt$ is the time taken

Step II:
It does not have any direction. So it is a scalar quantity. Units of power is Watts.
$P = \dfrac{{Joule}}{{\sec }}$
$1Watt = Joule{\sec ^{ - 1}}$

Step III:
Since units in physics are the quantities that have some value or magnitudes so they are standard for measurement of physical quantities.
In S.I. base its units are $kg{m^2}{s^{ - 3}}$
Other units of power are $erg/s$ and foot pound per minute.

Step IV:
This question has more than one answer.
So option A and C is the right answer.

Note: Sometimes the power can be mixed with energy. But they both are completely different. Energy is the total amount of work done on any object or system. But power is how fast that activity or work can be done. It is known that energy can not be created or destroyed but transformed from one form to another. So power is actually the rate at which the energy is transferred. It is already mentioned that power depends on the work done, so if in any system work is done at different rates, the value of power will also be different.