## Rest Mass?

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

Annalyn Diaz 1J
Posts: 61
Joined: Fri Sep 28, 2018 12:15 am

### Rest Mass?

During lecture Dr. Lavelle said that the De Broglie equation only works if the particles have “rest mass”. Can someone clarify what that means?

isarose0
Posts: 62
Joined: Fri Sep 28, 2018 12:15 am

### Re: Rest Mass?

Rest mass is when an "object" is not in motion, has mass. Therefore, electrons, protons, etc. have rest mass because they still have measurable mass when they are not moving (as if you were holding one). Photons do not have rest mass because they primarily exist in motion.

Jessica Helfond 2F
Posts: 60
Joined: Fri Sep 28, 2018 12:16 am

### Re: Rest Mass?

In simple terms, resting mass is just when an object has mass when it's stationary. Hope this helped!

705088777
Posts: 37
Joined: Fri Sep 28, 2018 12:18 am

### Re: Rest Mass?

Just think of problems in physics where an object is at rest. This means the velocity=0 because the object is not moving. So in this case, it means the mass of electrons when nothing is moving.

Erin Nash - 4G
Posts: 29
Joined: Fri Sep 28, 2018 12:27 am

### Re: Rest Mass?

An object that has rest mass is an object that's mass can be calculated when it is in rest. He used this in the context of light, since it is never at rest and therefore does not have rest mass.