How do you find velocity given weight and momentum?

The of a machine determines its "usefulness." a. input force b. output force c. mechanical advantage

Two resistors r1 and r2 may be connected either in series or parallel across an ideal battery with emf ε. we desire the rate of energy dissipation of the parallel combination to be 8.75 times that of the series combination. if r1 = 105 ω, what are the (a) smaller and (b) larger of the two values of r2 that result in that dissipation rate?

This is for my 8th grade science class, i really don’t understand. can someone me? , lol.