The overall change in velocity is just 20m/s.
A method of investigation in which a problem is first identified and observations, experiments, or other relevant data are then used to construct or test hypotheses that purport to solve it.
An electromagnet is made from a coil of wire which acts as amagnet when an electric current passes through it. Often anelectromagnet is wrapped around a core of ferromagnetic material like steel, which enhances the magnetic field produced by the coil.