The physics questions submitted to an 'ask a scientist' website were classified with respect to field of interest in physics, type of requested information in the question (factual, explanatory, etc.), and motivation for asking the question (applicative or non--applicative). In addition, differences in the number of females' and males' questions in these classifications were determined. Analysis of 995 physics questions submitted to the website indicated that modern physics questions (30.7%) were the most frequent while vibrations and wave motion questions (3.3%) were the least frequent. More than half of the questions (57.8%) were submitted to request factual information. Motivation to ask a question was inferred from the question, and was generally not related to direct and/or personal application. There were obvious differences in the number of questions asked by females and males: 84.7% of questions were asked by males while 15.3% were asked by females. However, significant gender differences were not observed in field of interest in physics, type of information requested in the question, and motivation for asking the question.