Earth pulls downward on a pen, of mass m, which is sitting on a table; the magnitude of the force is mg. If that is called the action force, what is the reaction force?

Aregion of space in which a measurable gravitational force is indicated by the force exerted on a test mass is called

Aball is thrown vertically upwards from the top of a tower with a speed of 100m/s.it strikes the pound near the base of the tower after 25sec . the height of the tower is

Ineed to answer this problem but i lack in knowledge, what should i study to answer this problem? i have never used derivatives in a physics problem so i'm not sure what's happening and i can't find videos explaining.