How does the hand crank flashlight prove the law of conservation of energy to be sure?

Astronomers discover an exoplanet (a planet of a star other than the sun) that has an orbital period of 3.87 earth years in its circular orbit around its sun, which is a star with a measured mass of 3.59 x 1030 kg. find the radius of the exoplanet's orbit.

Ahydroelectric plant takes energy from water and turns it into electrical energy. what are the transformations of energy in the water molecules that are used in the process of generating electricity this way?

What is the weight of a feather (mass = 0.0001 kg) that floats through earth's and the moon's atmospheres?