## 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?

Kelvin Chung 1C
Posts: 50
Joined: Sat Aug 24, 2019 12:15 am

### Re: Units

Do we need to know the SI unit equivalents for each term, like the joule?

AniP_2D
Posts: 95
Joined: Sat Aug 17, 2019 12:17 am

### Re: Units

Kelvin Chung 1C wrote:Do we need to know the SI unit equivalents for each term, like the joule?

I am not sure if you need to know them, but for the quantum section it would extremely helpful to know that a J is equal to kg*m^2*s^-2

Mellanie Gamero 4D
Posts: 10
Joined: Tue Oct 01, 2019 12:16 am

### Re: Units

I'm sure that it is important that you know the proper SI units for each term because there will be many problems which can be solved by canceling out, thus helping you find a corresponding answer for that problem in the simplest form.

Drew Myers 4G
Posts: 100
Joined: Sat Aug 17, 2019 12:17 am

### Re: Units

Will there ever be a time where we need to use megagrams or gigagrams or will we likely only go as big as kilograms?

Veronica Lu 2H
Posts: 89
Joined: Wed Sep 18, 2019 12:18 am
Been upvoted: 1 time

### Re: Units

I think for the most part it would only go as far as kilograms, but in any case, if megagrams and gigagrams were necessary I think we would be provided a formula sheet to convert the numbers.

GEOVANNAO_3F
Posts: 49
Joined: Fri Aug 30, 2019 12:17 am

### Re: Units

If you ever forget unit conversions just remember:

K- King
H- Henry
D- Died
U- Unusually
D- Drinking
C- Chocolate
M- Milk

PriscillaLi_3G
Posts: 63
Joined: Fri Sep 27, 2019 12:30 am

### Re: Units

Is it necessary that we put in the units while showing our work?