CAPE Physics Unit 1 · 2010 · Paper 1 · Question Q40

A gas contains N molecules. The speeds of the molecules are C_1, C_2, \dots, C_N. Which of the following equations can be used to determine the r.m.s speed of the molecules?

1. (A)\sqrt{\frac{C_1 + C_2 + \dots + C_N}{N}}
2. (B)\frac{C_1^2 + C_2^2 + \dots + C_N^2}{N}
3. (C)\frac{(C_1 + C_2 + \dots + C_N)^2}{N}
4. (D)\sqrt{\frac{C_1^2 + C_2^2 + \dots + C_N^2}{N}}