2. The symbol for momentum is the letter (13 Points)
"p" and we are not sure why scientists use this symbol.
"M" since "m" is used for mass.
"O" since both "M" and "m" are already used for other quantities.
"V" since velocity is an important part of the concept.

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.