<u>Answer:</u>
The correct answer option is: True.
<u>Step-by-step explanation:</u>
Its true that if there is no linear equation to start with, you can isolate and substitute a variable that is squared in both the equation.
For example, for the given non linear equation, start by dividing both sides by coefficient of the variable.
Once you do that and isolate a variable, continue solving by substituting that variable into the other equation.
In a mechanical system, it is a law that energy should be conserved. In this case, what is the initial energy should be equal to the total energy after the motion happened. We do as follows:
PE(at rest) = KE(during motion) + PE(after motion)
51450 J = KE(during motion) + 32781 J
KE(during motion) = 18669 J