Question

a mango on a tree possesses potential energy, when falling the potential energy is converted to kinetic energy. what is the value of the potential energy at the point the mango hangs on the tree?​

Answer 1

The potential energy of an object that is lifted a distance h from the ground is:

U = m*g*h

where m is the mass of the object, g is gravitational acceleration and h is the distance between the object and the zero in our vertical axis. (we suppose that the zero coincides with the ground)

Now, something interesting here is that we can "choose" where the zero is.

For example, if we put a table under the tree, the distance that the mango can fell will be smaller than h, so not all the potential energy will be transformed into kinetic energy unless we change the zero in our vertical axis such that the new zero coincides with the height of the table.

This means that we can have a lot of different values for the potential energy of the mango when it hangs on the tree.

This can be useful for example, if we want to calculate the potential energy with respect to 10cm under the mango, then when we have the potential energy equal to zero, we can obtain the exact kinetic energy of the mango in that point and then the velocity of the mango in that point, which may be useful in some situations.