1. The problem statement, all variables and given/known data 2. Relevant equations W = -U for conservative forces F = qV x B = qvBsinθ W = Fd for conservative forces K = 1/2mv^2 sinθ = 1 for 90° angles E1 = E2 (conservation of mechanical energy) 3. The attempt at a solution W = -U -Fd = U E1 = E2 K = U K = -Fd = -qvBsinθd K =-qvBd -K/qd = Bv (1) K = (1/2)mv^2 ∴ v = sqrt(2K/m) Substitute into (1) -K/qd = B ⋅ sqrt(2K/m) K^2/q^2d^2 = B^2 ⋅ (2K/m) mK/2q^2d^2 = B^2 B = sqrt(mk/2q^2d^2) Why is two in the denominator rather than in the numerator? Is my method invalid? If so, where can I improve? Thanks in advance.