particle has 17.5 joules of kinetic energy and 12.5 joules of gravitational potential energy at one point during its fall from a tree to the ground. An instant before striking the ground, how much mechanical energy — rounded to the nearest joule — does the particle have?

Em = 30 J

Explanation:

The principle of conservation of mass and energy is one of the most important in physics, it establishes that energy cannot be created just by transforming it.

Therefore, the mechanical energy at a point is the same throughout the movement, only in some parts it will be kinetic, in others potential and in the intermediate points a mixture of the two, but the total value is always the same.

           Em = K + U

            Em = 17.5 + 12.5

            Em = 30.0 J

At the point just before touching the ground the mechanical energy is the same Em = 30 J