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In support of all the students who are displaced from school due to the Corona virus. Access to physics zone and chemistry zone lessons are now available free of charge. This will be maintained at least through August 1st 2020. Learn and be well.

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Trigonometry Method

Since this method uses only values, it can be used to prove conservation of momentum even if the drawing is not to scale.

component vectors animation


This animation shows the collision of two asteroids and an analysis of the total momentum before and after the collision. Since the two total momenta are identical we can say that momentum is conserved.
  1. Calculate the momentum (m�v) of each object.
  2. Use trig functions and the given angles to calculate X and Y components of the momenta.
  3. Compare the total momentum in the X direction before and after the interaction (collision, explosion, attraction, repulsion).
    • Combine the X components of the momenta before the collision (Total momentum in the x)
    • Combine the X components of the momenta after the collision ()
    • They should be equal in magnitude and direction
  4. Compare the total momentum in the X direction before and after the interaction (collision, explosion, attraction, repulsion).
    • Combine the Y components of the momenta before the collision (Total momentum in y before)
    • Combine the Y components of the momenta after the collision (Total momentum in y after)
    • They should be equal in magnitude and direction
  5. By comparing the X and Y components you have already shown that momentum is conserved but you could go one step farther and compare the magnitude and direction of the total momentum vectors before and after the collision.  If they are identical then momentum is conserved.