Which is the best example of potential energy?
holding a basketball in the air
rolling a ball across a flat table
flowing electric current through a wire
turning on a flashlight in a dark room

Before coming into conclusion first we have to understand potential energy.The potential  energy of a body is defined as the energy possessed by a body due  to its position and configuration.

There are  generally two types of potential energy.One is gravitational potential energy and the other one is elastic potential energy.The former one is due to the position of the body at a certain height from the surface of earth.The latter one is due to the change in  configuration of the body.

There is also electric potential energy which is stored  inside the electric filed of charge particles at rest.

The first example is holding a basket ball in air.As the body is at certain height from earth surface ,hence it has gravitational potential energy which is a best example of potential energy.

The second one is a rolling ball across a flat table.It has both rotational kinetic energy due to its rolling motion as well as potential energy due to its position.

The third one  can't be considered as it is electric in nature.

The fourth one is turning on a flashlight in a dark room.The light is due to the heating effect of electric current. so it is not gravitational in nature.

Hence option  one is the correct answer.

no. dot product   =0 when vecs at right angles

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