Social Q&A allows people to ask and answer questions for each other and to solve problems in everyday life collaboratively. The purpose of the current study is to understand the motivations and strategies of answerers in social Q&A. Thus, three research questions were investigated: 1)Why do answerers participate and contribute in social Q&A? 2)What strategies do they use to provide effective answers in social Q&A? 3)What are the relationships between motivations and strategies? The domain of health is chosen because health is one of the most popular topics that people search information and support online. A model of answering behaviors has been proposed with a composition of 10 motivations and 32 strategies related to five steps of answering behaviors - question selection, question interpretation, information seeking, answer creation and answer evaluation. Two research methods - a survey and content analysis - were used. A survey questionnaire was distributed to top answerers and recent answerers in the health category of Yahoo! Answers. Answers of the survey participants were additionally collected in order to analyze the types of health messages and the sources of the answers. Altruism was found to be the most influential motivation, followed closely by Enjoyment and Efficacy. Answerers select questions based on their confidence or interest in the topic of the question. When interpreting questions, answerers believe that they understand the question most of the time. When seeking information for answers, most of the sources of answers are from the answerers' own information and experiences. When creating answers, accuracy and completeness are the most frequently used criteria for evaluating information sources. When evaluating answers, answerers review responses to their answers from questioners, other answerers, and other members in Yahoo! Answers. Additionally, motivations and strategies of all participants, top answerers, and health experts and the relationship between motivations and strategies are reported. Findings from the current study have practical implications for promoting the use of social Q&A as well as other similar Q&A services. The other important research implication is its contributions to the body of knowledge on information providing behaviors.