$1.$ The electromagnetic force is responsible for: a$.$ Attraction of protons within the nucleus b$.$ Repulsion of electrons c$.$ Nuclear decays in which electrons are ejected from the nucleus d$.$ Northern lights $2.$ The force of gravity on the Moon by the Earth is: a$.7\mathrm{.}6$ x $1028$ N b$.2\mathrm{.}0$ x $1020$ N c$.3\mathrm{.}0$ x $1030$ N d$.4\mathrm{.}0$ x $1040$ N $3.$ What is the gravitational potential energy of the moon due to its position relative to the Earth? a$.-2\mathrm{.}77$ x $1032$ J b$.-1\mathrm{.}98$ x $1020$ J c$.-7\mathrm{.}62$ x $1028$J d$.-4\mathrm{.}60$ x $1030$ J $4.$ An object in a gravity well will have: a$.$ Negative gravitational potential energy. b$.$ Negative kinetic energy. b$.$ A circular orbit. d$.$ Positive total energy.