Two brothers, frank and dion, are on roller skates and standing still when they push off from one another. frank's mass is 103.4 kg. dion's mass is 51.6 kg. after they push off, frank has a velocity of -7 m/s. what will dion's velocity be?

Aresistor with an unknown resistance is connected in parallel to a 9 ω resistor. when both resistors are connected in parallel to an emf source of 21 v, the current through the unknown resistor is measured with an ammeter to be 4 a. what is the resistance of the unknown resistor? answer in units of ω.