Which type of particle has a charge of 0 and a mass number of 1?

Oxygen and hydrogen gas are at the same temperature t. what is the ratio of kinetic energies of oxygen molecule and hydrogen molecule if oxygen is 16 times heavier than hydrogen.

To a of 4 x hz is 1. 0. mm nm nm

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.