Question

质量为0.5kg的物体,从离地面36m高处,由静止开始加速下落,经3s落地,求

Answer 1

h = 0.5 a t^2 => a = 2h / t^2 = 2×36m/(3s)^2 = 8m/s^2mg - f = ma => f = m(g-a) = 0.5kg × (10-8)m/s^2 = 1N