Consider the following systems: I) water behind a dam; II) a swinging pendulum; III) an apple on an apple tree; IV) the space shuttle in orbit. In which of the systems is potential energy present?

The potential energy are present in number I), II), and III).

Explanation:

The potential energy is the name given to the energy form when it is "stored", and it can manifest at any time, for example, in the form of movement, and the potential energy is derived from conservative ((A force is said to be conservative when their work is independent of the trajectory) forces, the body's trajectory does not interfere with the work performed by the force, what matters is the final and initial position, meaning that the path does not interfere in the final value of the variation in potential energy. This way,

I) "water behind a dam" We can consider the Hydraulic energy or hydropower which is the energy obtained from the potential energy of a body of water. The way in which it manifests itself in nature is in water flows, such as rivers and lakes, and can be used through a drop or waterfall

II) "a swinging pendulum" we can say that at the point of maximum amplitude of the pendulum, the potential energy is maximum;

III) "an apple on an apple tree" The potential energy of the apple depends on the apple height in relation to the ground, the force of gravity and the apple mass (Ep = mgh), which results on the maximum gravitational potential energy of the apple;

IV) "the space shuttle in orbit" there is no gravitational potential energy because the gravitacional force is 0.  

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