Matt asked in Science & MathematicsPhysics · 1 month ago

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

Relevance
• 1 month 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.

• Anonymous
1 month ago

mechanical energy conservation:

KE1 + PE1 + w = KE2 + PE2

where

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

finally

PE1 = PE2