What must act upon an object to make it start or stop?

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?

If you place a magnet under a clear dish, and sprinkle iron fillings over it, above what part of the magnet will most of the fillings gather

Which is an example of an exothermic process?