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Joules units

Posted: Fri Oct 18, 2019 12:39 am
by Jedrick Zablan 3L
Hello can anyone explain to me why Joules in Planck's Constant is kg x m^2 x s? Thanks.

Re: Joules units

Posted: Fri Oct 18, 2019 1:34 am
by andrewcj 2C
In the formula E = hv, E is measured in Joules and v is measured in Hz, or s^-1. By dimensional analysis, we see that by multiplying kg x m^2 / s by 1/s, we get a units of kg x m^2/s^2. Since Joules is a measure of energy/work, it is equivalent to force x distance. Breaking this down further, force is equivalent to mass x acceleration, which results in units of kg x m/(s^2). Multiplying this by distance gives you kg x m^2/s^2, which is the same as the units for the right side of the E = hv equation.

Re: Joules units

Posted: Fri Oct 18, 2019 9:21 am
by KaleenaJezycki_1I
JedrickZ_3L wrote:Hello can anyone explain to me why Joules in Planck's Constant is kg x m^2 x s? Thanks.


Joules in Planck's Constant is expressed as such because it helps for unit cancellation, depending on what you are solving for one of these two expressions will be easier to visually see how you obtain your final units.

Re: Joules units

Posted: Sat Oct 19, 2019 7:42 pm
by Jenna Ortiguerra 4G
Joules in Planck's Constant can either be expressed by 6.626 x 10^-34 J.S. or 6.636 * 10^-34 kg*m^2*s^-1. Typically, choosing between 6.636 * 10^-34 kg*m^2*s^-1 and 6.626 x 10^-34 J.S. is situational, in which the one that would provide the easiest cancellations would be the best option to use.

Re: Joules units

Posted: Thu Oct 31, 2019 9:53 am
by 505106414
So the units are essentially equivalent to each other?

Re: Joules units

Posted: Thu Oct 31, 2019 10:18 am
by Nathan Nakaguchi 1G
Planck's Constant's units are J * s (joules times seconds) not necessarily just joules, thats why the Planck's units are (kg m^2 s^-2) * (s) = kg m^2 s^-1.

Re: Joules units

Posted: Sun Dec 08, 2019 9:15 am
by Mai V 4L
Does anyone have a video they think is aa good reference for this topic?