## Units

$E=hv$

Henry Krasner 1C
Posts: 64
Joined: Fri Sep 28, 2018 12:15 am

### Units

What unit does J.s^(-1) translate into, and how would we use this new unit to calculate the correct unit for finding wavelength, in say, the equation of λ=h (unit of J.s^(-1)/mv?

Summer de Vera 2C
Posts: 65
Joined: Fri Sep 28, 2018 12:16 am

### Re: Units

It translates into kgm^2/s because a joule is kgm^2/s^2, and if you divide it by 1/s, it gets to this unit.

804994652
Posts: 68
Joined: Fri Sep 28, 2018 12:26 am

### Re: Units

1 joule = 1kg·m^2·s^-2
If you divide it by s-1. One of the 's' cancels out and you get 1kg·m^2·s^-1.

Jchellis 1I
Posts: 61
Joined: Fri Sep 28, 2018 12:15 am

### Re: Units

Its important to remember that we use kg instead of grams for SI units. I know I always forget!

Tatum Keichline 2B
Posts: 64
Joined: Fri Sep 28, 2018 12:26 am

### Re: Units

Joule is kgm^2/s^2, but multiplying my 1/s cancels one of the s units, making kgm^2/s

Mhun-Jeong Isaac Lee 1B
Posts: 54
Joined: Fri Sep 28, 2018 12:17 am

### Re: Units

Just another reminder too is that Herz = s^-1. I find it helpful to convert Hz to s^-1 so that if units are being multiplied or divided, it's easier to see how things cancel out.

Daniel Chang 3I
Posts: 33
Joined: Fri Sep 28, 2018 12:23 am

### Re: Units

a Joule multiplied by 1/s is composed of 1kgm^2/s in its simplest form

105002507
Posts: 30
Joined: Fri Sep 28, 2018 12:15 am

### Re: Units

When do we use kg?

Amy Dinh 1A
Posts: 62
Joined: Fri Sep 28, 2018 12:23 am

### Re: Units

105002507 wrote:When do we use kg?

We use kg when we are calculating energy, since the units are in jules (kg·m^2·s^-2)

lukezhang2C
Posts: 59
Joined: Fri Sep 28, 2018 12:18 am

### Re: Units

It should follow e=mc^2 for photons, which is kgm^2/s^2

duverge_maciel
Posts: 21
Joined: Fri Sep 28, 2018 12:16 am

### Re: Units

If a calculation is in Hz, does that mean it will always be a positive value?