The formula for kinetic energy is KE=frac12mv2KE = \\frac{1}{2}mv^2KE=frac12mv2. Solve for vvv (positive value).
v=sqrtfrac2KEmv = \\sqrt{\\frac{2KE}{m}}v=sqrtfrac2KEm
v=frac2KEmv = \\frac{2KE}{m}v=frac2KEm
v=sqrtfracKE2mv = \\sqrt{\\frac{KE}{2m}}v=sqrtfracKE2m
v=2KE−mv = 2KE - mv=2KE−m