## Velocity [ENDORSED]

$c=\lambda v$

Josh Moy 1H
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### Velocity

Is Velocity (m/s) the same as speed?

Deap Bhandal L1 S1J
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### Re: Velocity

In this case it's very similar. Velocity is just speed with direction. Sometimes a negative sign will denote a leftward direction and a positive will denote a rightward direction, but nowhere is this set in stone. As long as the reference point is kept constant throughout the experiment, there should be no problem. But do not get confused with the other v, which stands for frequency.

Chem_Mod
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### Re: Velocity

Basically, for a physics class no but for Chem 14A yes.
Hope this helps! -Ajith :D

Matt_Fontila_2L_Chem14B
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Joined: Fri Sep 29, 2017 7:07 am

### Re: Velocity

If we can use them interchangeably for this class, does that mean we can use the speed of light in a vacuum (2.988x10^8 m/s) in De Broglie's Equation?

λ = h/m*v

Would we then just need the mass to determine the wavelength?

Katie Lam 1B
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Joined: Fri Sep 29, 2017 7:06 am

### Re: Velocity

I went to Dr. Lavelle's office hours today and learned that De Broglie's equation cannot be applied to light or electromagnetic radiation. It can only be applied to particles with rest mass, like electrons, so you can't use the speed of light in De Broglie's equation.

Kathleen Vidanes 1E
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### Re: Velocity

After reading this, I am still a bit unsure of how the speed of light relates to velocity. Are they directly related / inversely related? Is speed of light (3.00x10^8m.s-1) interchangeable with velocity?

Bansi Amin 1D
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### Re: Velocity

The speed of light can be used as velocity for massless particles like photons. Not too sure about the whole relationship part.

Kyung_Jin_Kim_1H
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### Re: Velocity

I'm still confused. Can we use the speed of light as our velocity element when the direction part of the vector component is negligible in our calculations?

CalebBurns3L
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### Re: Velocity  [ENDORSED]

Yes, the speed of light can be considered a velocity, speed is simply the magnitude of velocity. However, that doesn't mean you can use it has the velocity component in De Broglie's equation. That equation is for particles with mass, not for light waves/photons.

Michelle Lu 1F
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### Re: Velocity

Speed is basically the absolute value of velocity, because velocity is speed but with direction. They both have the same units m/s.

Sheel Shah 1H
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Joined: Fri Sep 29, 2017 7:04 am

### Re: Velocity

velocity is the absolute value of speed in calculus terms; essentially speed simply analyses magnitude whereas velocity takes into account both magnitude and direction. Velocity is a vector and speed is a scalar. These details are more important in physics and will not play a crucial role in analyzing the speed of an ejected electron using the kinetic energy equation in the photoelectric effect.

Hope that helps! :)

Richard Braun 1I
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### Re: Velocity

Velocity is speed with a direction.

Kaelie Blanes-Ronda 2L
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### Re: Velocity

Speed and velocity are pretty much equals except that the speed doesn't tell you the direction the person/object is moving in relatively to the starting point x=0. For example a car can be traveling at a speed of 40 miles per hour but that doesn't tell you whether the car is heading west or east. The velocity which is -40 miles per hour would indicate west or +40 miles per hour would indicate east.

Troy Tavangar 1I
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Joined: Fri Sep 29, 2017 7:04 am

### Re: Velocity

Velocity affects direction while speed disregards direction all together. For example, 10 mph west is a velocity while 10 mph is speed.

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