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# Calculate the wavelength of a baseball?

Okay, I don't know what I'm doing wrong here... I'm studying for a midterm. Here's the question on the review packet:

Calculate the wavelength of a baseball (m = 155 g) moving at 32.5 m/s.

I keep getting that the wavelength is 1.389*10^-34

The answer that I have to choose from are:

A) 1.32 × 10-34 m

B) 3.57 × 10-32 m

C) 2.15 × 10-32 m

D) 7.60 × 10-36 m

E) 2.68 × 10-34 m

So I'm inclined to say the answer's 'A', but why I can't get that exact value is beyond me. I thought it was a rounding issue, but I'm thinking there's something I'm doing wrong.

Thanks, once again Chemistry masterminds.

m w

I forgot to convert mass in grams to kilograms.... Totally forgot. Thanks, again! :)

### 1 Answer

- Dr WLv 71 decade agoFavorite Answer
you're trying to calculate the DeBroglie wavelength.

λ = h / (mv) x √ (1 - v²/c²)

and that relativistic term √ (1 - v²/c²) ≈ 1 at velocities <<< speed of light.

so that...

λ ≈ h / (mv) = (6.626x10^-34 kg m²/s) / (0.155kg x 32.5 m/s) = 1.32x10^-34 m/s

********

looks to me as if your using 7x10^-34 as the value for plancks constant. why is that?