An atomic nucleus of radon initially moving at 530 m/s emits an alpha particle in the direction of its velocity, and the new nucleus slows to 410 m/s. If the alpha particle has a mass of 4u, and the original nucleus of radon had a mass of 222u, what speed does the alpha particle have when it is emitted?
2 answers
u is the SI unit for atomic mass. Even though it is not in kg, you don't need to do the conversion since the units of mass will cancel.
222 * 530 = original momentum
4 v + 218 * 410 = final momentum
original momentum = final momentum
4 v + 218 * 410 = final momentum
original momentum = final momentum