How much voltage is required to make 4 amperes flow through a resistance of 20 ohms?

An electron is traveling with initial kinetic energy k in a uniform electric field. the electron comes to rest momentarily after traveling a distance d. (a) what is the magnitude of the electric field

If the work required to stretch a spring 3 ft beyond its natural length is 15 ft-lb, how much work is needed to stretch it 27 in. beyond its natural length?

Which component of the earth’s atmosphere is decreased due to photosynthesis?