Quantum phsics and x-ray physics

[whiteshado]

is there anyone on here who could help me out with either of these?

 

[whiteshado]

heres a sample question
Calculate the de Broglie wavelength of a 5,000 kg truck traveling at 80 kph. (Round answer to nearest hundredth.)

 

[StatusX]

Help you with what? Are you doing a project? Or do you just have a bunch of questions? Just post your questions and people will help you with them. For the one above, that's just plug and chug. The formula for deBroglie wavelength is p = h/λ, where h is Plancks constant.

 

[whiteshado]

λ=5.97x e-39
tahts the answer now how did i get it
and i have a lot of questions like this i just don't know how they are done

 

[whiteshado]

ill post 2 mroe then i have to go for a while
Calculate the uncertainty of the velocity of a particle confined to a space of 10-9 m if the particle is an electron
(me = 9.1 · 10-31 kg)

delta v=__________m/sec

and


Calculate the uncertainty of the velocity of a particle confined to a space of 10-9 m if the particle is a proton
(mp = 1.7 · 10-27 kg)

delta v=___________m/sec


tahnks for your help
btw if you didnt get this already i want how to get the answer not the answer

 

[StatusX]

There are no concepts here. You just find p (which is m*v), look up the value for h, plug them in, and solve for λ. Feel free to ask any other questions right here, you don't need to ask for permission.

 

[StatusX]

Are you asking where the formula comes from? If so, that's a little complicated, but I can give you a rough sketch.

If you're asking how to plug numbers into a formula, you need to take a lot more math classes before you get into QM.

 

[whiteshado]

There are no concepts here. You just find p (which is m*v), look up the value for h, plug them in, and solve for λ. Feel free to ask any other questions right here, you don't need to ask for permission.

m and v mass and velocity
is that right? so the answer would be 5000*80*6.63e-34 correct? but it doesn't get the correct answer

and yes i know how to as you say "plug and chug"

 

[StatusX]

p=h/λ, so λ=h/p. Why are you doing these problems if you're still not comfortable with basic high school physics and math?

 

[whiteshado]

p=h/λ, so λ=h/p. Why are you doing these problems if you're still not comfortable with basic high school physics and math?

that still doesn't get the correct answer
λ=h/p
6.63e-34/(5000*80) =λ doesn't get the correct answer so either your wrong or you just don't get what I am asking for can you do the question if so past your work on this page that's all i ask for

 

[O_o]

Make sure everything is in SI units before you start solving.

 

[Gokul43201]

that still doesn't get the correct answer
λ=h/p
6.63e-34/(5000*80) =λ doesn't get the correct answer so either your wrong or you just don't get what I am asking for can you do the question if so past your work on this page that's all i ask for

No, whiteshado : StatusX is perfectly correct.

You need to learn the following things first (way before you do Quantum Physics) :

1. Basic algebra and arithmetic
2. Units and dimensions

take care of these and you'll be able to handle the first problem.

We will not provide answers/solutions to your problems. That is not what this forum is meant for. If you need help with specific concepts, ask away, but if you have homework to do, we can not help unless you show what effort you have made.

 

[whiteshado]

no i have the answers i posted the answer
λ=5.97x e-39
but how did i get it?

 

[whiteshado]

ok how about a simpler one i need the equation for finding the frequency for a wavelength

 

[dextercioby]

What's the SI unit for velocity ?

Daniel.

 

[juvenal]

no i have the answers i posted the answer
λ=5.97x e-39
but how did i get it?

The answer you give is meaningless. You have no units (unless that x you have is not "times" but some constant with a unit). Wavelength is not dimensionless.

 

[whiteshado]

Calculate the de Broglie wavelength of a 5,000 kg truck traveling at 80 kph
λ=5.97 e-39m

 

[dextercioby]

Alright.Now did u find out how to derive this result...?

Daniel.

 

[whiteshado]

sigh taht is what i am trying to find out... but no one reads on this fourm

and someone said I am am just trying to get people to do my homework well how many people who want their homework done post the answer to their questions

 

[dextercioby]

You've been told that

$$\lambda \ \left(\mbox{m}\right)=\frac{h \ \left(\mbox{Kg}\cdot\frac{\mbox{m}}{\mbox{s}^{2}}\cdot\mbox{m}\cdot\mbox{s}\right)}{p \ \left(\mbox{Kg}\cdot\frac{\mbox{m}}{\mbox{s}}\right)}$$

Now plug the values paying attention to the units.Planck's constant is given in $\mbox{J}\cdot\mbox{s}$ which u can show to be equal to $\mbox{Kg}\cdot\frac{\mbox{m}}{\mbox{s}^{2}}\cdot\mbox{m}\cdot\mbox{s}$.

U need to find the truck's momentum in SI units.Basically,u need to convert its speed from $\frac{\mbox{Km}}{\mbox{hr}}$ to $\frac{\mbox{m}}{\mbox{s}}$.

Daniel.

 

[StatusX]

You need to have everything in SI units. That means m, s, kg, etc. Whenever you see a km, turn it into a m. When you see an hour, make it a second. For example, 5 km would have to be put into the formula as 5000 m.

Here's another way to do it. Write out h/p with units on all the numbers. You'll get something like 5 m/km s/hr... m. Everything must be turned into a number except the final unit you want, in this case, 'm'.

Why are you doing these problems? It's bad enough when high school students are told to plug numbers into a formula without any understanding, but you don't even seem to be ready to do that.

 

[whiteshado]

wow finally some real help taht is exatly what i wanted

 

[whiteshado]

woo i got the answer