Mechanical Engineering is a popular optional subject for the UPSC examination. To effectively answer questions related to this subject, it is important to include specific keywords and phrases that demonstrate your knowledge and understanding. These keywords and phrases can help you structure your answer and highlight important points. Here are some key pointers to consider:

1. Technical Terminology:
- Include technical terms related to mechanical engineering such as thermodynamics, fluid mechanics, heat transfer, kinematics, etc.
- Use keywords that are specific to the question being asked. For example, if the question is about the working of a steam turbine, include keywords like Rankine cycle, turbine efficiency, condenser, etc.

2. Concepts and Principles:
- Clearly explain the fundamental concepts and principles related to the question.
- Use phrases like "According to the first law of thermodynamics," "In accordance with Bernoulli's principle," etc., to demonstrate your understanding of the subject matter.
- Discuss the relevant equations and formulas, and explain how they are applied in the given context.

3. Problem-solving Approach:
- Showcase your problem-solving skills by including keywords like analysis, design, optimization, efficiency, etc.
- Describe the steps involved in solving a particular problem or designing a mechanical system.
- Use phrases like "To tackle this problem, we can use the following approach," "By applying the principles of statics and dynamics, we can determine," etc.

4. Real-world Applications:
- Provide examples of real-world applications of the concepts being discussed.
- Include keywords that relate to industries or technologies where mechanical engineering principles are applied, such as automotive, aerospace, power plants, robotics, etc.
- Highlight the significance of the topic being discussed in the field of mechanical engineering.

By incorporating these keywords and phrases in your answers, you can demonstrate a strong understanding of the subject and effectively communicate your knowledge to the examiner. Remember to structure your response using headings and bullet points to make it visually appealing and easy to follow.