Question

A 0.100 kilogrom apple hangs 1.5 meter above the ground. Ignroing frictional effects, the total mechanical energy of the apple is?

Answer 1

The total mechanical energy is equal to the apples kinetic energy plus the potential energy.:
\[E _{mechanical}=E_{kinetic}+E_{potential}\]
As the apple is standing still the kinetic energy is equal to 0.
\[E _{kinetic}=\frac{ 1 }{ 2 }mv ^{2}\]
Therefor you only have to calculate the potential energy:
\[E_{potential}=mgh\]
m is the mass, g the acceleration due to gravity and h the hight above the level you call 0 - in this case the ground.

So to sum up:
\[E _{mechanical}=E_{kinetic}+E_{potential}=\frac{ 1 }{ 2 }mv ^{2}+mgh\]
But as the velocity equals 0 we reduce to:
\[E _{mechanical}=E_{poteantial}=mgh\]