physics

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a proton (mass 1.67 x 10^-27 kg) with a velocity of 1.10 x 10 7 m/s collides with a motionless helium nucleus, and the proton bounces back with a speed of 6.00 x 10 6 m/s. The helium nucleus moves forward with a velocity of 4.00 x 10 6 m/s after the bombardment. What is the mass of the helium atom?

  • physics -

    momentum is conserved.

    initialmomentum=final momentum
    mHe*vhe + mp*Vp=mpVp' + mhe*vhe'

    solve for mhe.

    forward velocity is +, back velocity is -

    happy calculating

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