DeBroglie Equation Post Assessment

[gabbym]

If an electron (mass 9.11 x 10-31 kg) has an associated wavelength of 7.28 x 10-9 m, what is its speed? Is your answer reasonable, why?
Can someone help me with this problem? I think I am rearranging the equation wrong or something. I thought it should be v=h/m*wavelength, but I keep getting the wrong answer.

[yaosamantha4F]

That should be correct, although when you're plugging numbers into your calculator, make sure to put parentheses around (m*wavelength). It is not reasonable for an electron to be faster than the speed of light, but if the electron is below 10^5m/s, this may also be too slow to be reasonable.

[Grace Kim 1J]

Your formula is correct; After you rearrange the DeBroglie Equation to set it equal to the velocity, you get v = h/(wavelength) (mass). When you plug in the numbers into the equation, you should get 1.00 m.s^-1 as the answer.
It might be a simple calculation error!

h= 6.62608 x 10^-34 J.s
wavelength= 5.3 x 10^6 m
mass= 9.11 x 10^-31 kg

[404536963]

The answers above give you the correct answer, but just make sure that you use parenthesis in your calculator! I know that in my experience I sometimes get the wrong answer when I'm dividing by something like Planck's Constant, it can get confusing if you are dividing while multiplying by 10^34, so just make sure you're doing it in steps!

[904983525]

The answers above give you the correct answer, but just make sure that you use parenthesis in your calculator! I know that in my experience I sometimes get the wrong answer when I'm dividing by something like Planck's Constant, it can get confusing if you are dividing while multiplying by 10^34, so just make sure you're doing it in steps!

Thank you for this, I was having a problem too with my calculation.