## Units of Energy

$E=hv$

Katie Frei 1L
Posts: 64
Joined: Fri Sep 28, 2018 12:27 am

### Units of Energy

How is 1 Joule expressed in terms of SI base units? When would we convert J into SI base units in order to solve an equation?

Kate Chow 4H
Posts: 61
Joined: Fri Sep 28, 2018 12:28 am

### Re: Units of Energy

1 Joule = 1 kg * m^2 * s^-2, which can also be written as kg*m^2/s^2

You can convert Joules to SI units when you're using dimensional analysis to help you solve a problem. This could come in handy whenever you're solving for energy, as energy is often measured in Joules.

Ian Marquez 2K
Posts: 66
Joined: Fri Sep 28, 2018 12:16 am
Been upvoted: 2 times

### Re: Units of Energy

Also, putting Joules in terms of SI units can be especially handy when seeing if units make sense and cancel correctly. For example, in calculating wavelength for light, the kg, seconds, and one m cancel leaving your answer in m (meters).

monikac4k
Posts: 56
Joined: Fri Sep 28, 2018 12:25 am

### Re: Units of Energy

It is best to break down the units of a joule when you are also trying to calculate energy. Often times problems will try to trick you by giving velocity in miles/hour or they will give you mass in grams. When you approach a problem like this, it is important to know that you need values in kg and m/s in order to solve for energy in joules.

Imelda Mena 3I
Posts: 51
Joined: Thu Oct 02, 2014 3:00 am

### Re: Units of Energy

I personally always like to write out the SI units for Joules in order to make sure the units match with everything else and I am not using the wrong variable. However in terms of when you actually NEED to write out the SI units, I would say whenever the question asks you to, otherwise there is no need.

Mallory_Podosin_1H
Posts: 31
Joined: Fri Sep 28, 2018 12:15 am

### Re: Units of Energy

The way that I remember the SI units for a Joule is by writing out the equations from physics

E = F*d
also F=ma
so,
J=(kg*m*(s^-2))*m
J=kg*m^2*s^-2