what would be the de Broglie wavelength of a helium atom (atomic weight=4.00u) moving at 100m/s?

Question

A) 2.00 x 10-9 m
B) 9.97 x 10-10 m
C) 9.97x10-7 m
D)1.66 x 10-36 m
E) 9.97 x 10-13 m
F) 1.66 x 10-19 m

Answer 1

B.
Planck's constant/ (mass*velocity) = (6.6262 * (10^(-34))) / (4 * 1.6606 * (10^(-27)) * 100) = 9.97561122 × 10-10 .

(The 1.6606*10^-27 refers to the atomic mass unit u.)

You can use the formula at http://scienceworld.wolfram.com/physics/deBroglieWavelength.html with Planck's constant at http://scienceworld.wolfram.com/physics/PlancksConstant.html