Question

What is the speed of a 50 g rock if its de broglie wavelength is 3.32x10^-34m?

Answer 1

We can find the momentum of the rock by using De Broglie's relationship:
$p= \frac{h}{\lambda}$
where
p is the momentum
h is the Planck constant
$\lambda$ is the De Broglie's wavelength

By using $\lambda=3.32 \cdot 10^{-34} m$, we find
$p= \frac{6.6 \cdot 10^{-34} Js}{3.32 \cdot 10^{-34} m}=1.99 kg m/s$

The momentum of the rock is
$p=mv$
where $m=50 g=0.05 kg$ is the mass and v is its velocity. Rearranging the equation, we find the speed of the rock:
$v= \frac{p}{m}= \frac{1.99 kg m/s}{0.05 kg}=39.8 m/s$