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Need Formula

  1. Nov 19, 2006 #1
    Question - Two protons, seperated by a large distance, are fired directly at each other. The closest approach in this head-on collision is 3.0 x 10^14 m. One proton starts with two times the speed of the other. Assuming there is no delection from the original path, determine the initial speed of each proton.

    Solution - I read through my notes and text book but I couldnt find any way to connect speed with this question. Is there any specific equations to use?
  2. jcsd
  3. Nov 19, 2006 #2


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    Conservation of energy.

    the total energy is [tex] {1 \over 2} m_1 v_1^2 + {1 \over 2} m_2 v_2^2 - {k q_1 q_2 \over r} [/tex] and it is conserved.
  4. Nov 19, 2006 #3
    So, since I don't know what the mass is or the speed, would I split the question up into two parts, the first being at collision so I can solve for mass since speed is zero. Then I can use the law of conservation of energy to find velocity at start?
  5. Nov 19, 2006 #4
    Actually, how would I solve that if there is 3 unknowns: mass, velocity, and charge?
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