A mechanical engineer works with the principles of motion, energy, and force. Usually a machine transforms one form of movement into another. Mechanical engineers design machines whose parts work safely, reliably, and efficiently. Mechanical engineers apply scientific methods to find answers to mechanical problems. Many laws and principles developed by scientists are used daily by the mechanical engineer. Mechanical engineers contribute to many industries and professions. Some mechanical engineers work in fields that don't typically require engineering. Efforts to clean and preserve the earth's environment have attracted many mechanical engineers to projects dealing with water, soil, and waste treatment. Mechanical engineers also work with doctors, therapists and other healthcare professionals to study how the human body works and design aids and instruments for mechanics. Mechanical engineers work in industry, consulting firms, academia and government research. Most mechanical engineers work in industry with equipment manufacturers, aerospace companies, utilities, and many other large and small businesses. Job responsibilities range from fundamental research and system design to power plant operations and quality control. Mechanical engineers earn good salaries. An entry-level engineer with a bachelor's degree can earn $40,000 per year. The median salary for an engineer is over $65,000. Earnings depend on experience and training. The government tends to pay its engineers slightly less than the going rate in the private sector. Large companies with top mechanical engineers typically offer comprehensive benefits packages. Benefits include health insurance, life insurance, paid sick leave, paid vacation and travel expenses..