## How do we get E=pv? [ENDORSED]

$\lambda=\frac{h}{p}$

Sue Xu 2K
Posts: 58
Joined: Fri Sep 29, 2017 7:06 am

### How do we get E=pv?

When deriving the DeBroglie equation we need the equation E=pv. Where do we get this equation?
Also, if p=mv then E=mv^2. What does this have to do with the Kinetic energy Ek=(1/2)mv^2?

Michael Koger 3K
Posts: 21
Joined: Fri Sep 29, 2017 7:07 am

### Re: How do we get E=pv?  [ENDORSED]

This equation comes from the definition of energy. 1 joule (the unit of energy) is defined as 1 N x m, or 1 [(kg x m^2)/s^2]. Momentum times velocity also yields [(kg x m^2)/s^2]. Therefore, the equation E = pv is merely a restatement of the units of energy.

The formula for kinetic energy is not used in the derivation of the de Broglie equation, so don't worry about it.

I hope this helped!

Diego Zavala 2I
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Joined: Fri Sep 29, 2017 7:07 am
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### Re: How do we get E=pv?

$E=mc^2$ and since C is the speed of light, we can rewrite the equation as $E=mv^2$. Since p=mv, E=pv.