A proton of mass 1.66x10-27 kg collides head-on with a helium atom at rest. The helium atom has a mass of 6.64x10-27 kg and recoils with a speed of 5x105 m/s. If the collision is elastic, what are the initial and final speeds of the proton and the fraction of its initial energy transferred to the helium atom?​ (pls help)​



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