What does it mean to say that the "net force" determines an objects acceleration?

Write the equation for momentum, first using symbols for the variables, then using words for the variables.

When the force acting on an object points at least partially in the direction of the motion the work done is considered to be negative

Does work output exceed work input when a machine is used? a) yes, it does, as machines create energy. b) it depends on the type of machine used. c) no, it doesn’t, as machines are inefficient. d) no, it doesn’t, as machines cannot create energy.