## 1J=1kg.m^2.s^-2

H-Atom ($E_{n}=-\frac{hR}{n^{2}}$)

Or Fisher 1I
Posts: 35
Joined: Fri Feb 02, 2018 3:00 am

### 1J=1kg.m^2.s^-2

Hi,
I am trying to understand how 1J=1kg.m^2.s^-2. How are these units equal to each other? Does anyone know the proof?
Thanks.

KateCaldwell 1A
Posts: 43
Joined: Fri Apr 06, 2018 11:02 am

### Re: 1J=1kg.m^2.s^-2

I'm not sure if I'm fully correct, but a Joule derives from a Newton (kg.m/s^2). Joules measures amount of work done on an object (mass) going through a distance of one meter. Which is why a Joule is a Newton times mass, so kg.m^2.s^-2.

nelquosey
Posts: 31
Joined: Fri Apr 06, 2018 11:02 am

### Re: 1J=1kg.m^2.s^-2

If you think about the equation for kinetic energy you see that Ek=(1/2)mv^2. (1/2) is a constant and has no units. Mass has units in Kg and velocity is measured in m/s. The equation asks you to square velocity and if you think about your exponent laws (m/s)^2 comes out to be m^2/s^2. This equation does not show divisibility, it alters the division of seconds and makes it a product by raising seconds to the negative power, and that is how you end up with J=Kgm^2s^-2. Hope that helped :)

Chem_Mod
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Joined: Thu Aug 04, 2011 1:53 pm
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### Re: 1J=1kg.m^2.s^-2

I hope the above post helps you see the connection between the units of energy and other units. I cannot say there is a proof because what you have said is the definition.