Why is it important to teach simple machine?

Which statement best explains why the overall charge on an atom is zero?

What is the magnitude of the gravitational force acting on the earth due to the sun?

Ball bearings are made by letting spherical drops of molten metal fall inside a talll tower-called a shot tower- and solidify as they fall. a-if a bearing needs 4.0 s to solidify enough for impact, how high must the tower be? b- what is the bearing's impact velocity?