Kim asked in Science & MathematicsPhysics · 3 months ago

What is this formula used for and how do you know when to cancel variables out? KE1  + PE1  + w = KE2  + PE2     ?

2 Answers

  • 3 months ago

    It is simply that energy is conserved.  All the original energy must exist after the action.  "Cancel variables out" is not a valid mathematical process.  You can perform any operation on both sides.  Add a value, subtract a value, multiply by a value and so on.  If any of these can make the problem simpler then that is what we mean by cancelling.

    ie if we know that PE1 = PE2 then KE1 + PE1 +w= KE2 +PE1

    subtract PE1 from BOTH sides ( "cancelling")

    KE1+w = KE2  That has simplified the problem for this specific case.

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  • Anonymous
    3 months ago

    mechanical energy conservation:

    KE1 + PE1 + w = KE2 + PE2 


    1 = initial state

    2 = final state

    KE = kinetic energy

    PE = potential energy

    W = work

    being (kinetic energy or work theorem):

    kinetic energy variation = work

    KE2 - KE1 = W

    on get:

    KE1 + PE1 + KE2 - KE1 = KE2 + PE2 


    PE1 = PE2


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