## Post-Assessment #34 [ENDORSED]

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

Alysia Garcia 1B
Posts: 40
Joined: Wed Feb 21, 2018 3:02 am

### Post-Assessment #34

In this problem:
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?
I got the answer 1x10^-5 m/s, but how would you determine if the speed is reasonable?

KateCaldwell 1A
Posts: 43
Joined: Fri Apr 06, 2018 11:02 am

### Re: Post-Assessment #34  [ENDORSED]

I believe a speed is reasonable if it is less than the speed of light (3.00x10^8 m.s^-1). Your answer seems to be correct then because it is much smaller than the speed of light.

Natalie Noble 1G
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Joined: Thu Feb 01, 2018 3:02 am
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### Re: Post-Assessment #34

This is awkward but you may want to recheck your calculations. The answer shouldn't be negative, it should be 1.00 x 10^5 m/s (if it were negative that would be an extremely slow electron). The reason 1.00 x 10^5 m/s makes sense is because the electron is moving slower that the speed of light, which makes sense (it is not possible to move faster than the speed of light).

Maya Khoury
Posts: 29
Joined: Fri Apr 06, 2018 11:03 am

### Re: Post-Assessment #34

I attached a picture below of me trying to find the speed for this problem but for some reason i always end up with a ridiculously large number. Can someone tell me what I'm doing wrong? I'm sure it's a stupid mistake lol

thank you !
Attachments

Chem_Mod
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### Re: Post-Assessment #34

Your denominator value should be more closer to 10-40 order of magnitude not 10-49

Mario Reyes 1C
Posts: 45
Joined: Fri Apr 06, 2018 11:04 am

### Re: Post-Assessment #34

Maya Khoury wrote:I attached a picture below of me trying to find the speed for this problem but for some reason i always end up with a ridiculously large number. Can someone tell me what I'm doing wrong? I'm sure it's a stupid mistake lol

thank you !

The denominator should be 10^-39, not 10^-49