4 ms·It should be 2*speed^2 for head on, no? The energy adds, not multiplies. Multiplying would change the unitsby 8note 2y agoIt should be 2*speed^2 for head on, no? The energy adds, not multiplies. Multiplying would change the unitsmike_hock 2y ago4*(speed^2) because the relative speed is doubled.hn8305823 2y agoyes, Oops!