What is the potential of a 10kg book that is placed on a shelf that is 2.5 meters high

Why is there friction between objects

In the image, the arrow is pointing to a celestial object. which attribute disqualifies the object from being a planet?

Afisherman notices that his boat is moving up and down periodically without any horizontal motion, owing to waves on the surface of the water. it takes a time of 2.20 s for the boat to travel from its highest point to its lowest, a total distance of 0.670 m . the fisherman sees that the wave crests are spaced a horizontal distance of 5.80 m apart. (a) how much is the wavelength? (b) find the period of the wave. (c) how fast are the waves traveling? (d) what is the amplitude a of each wave?