$887*/*/$:$\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_-88656$ : Explain the concept of friction and its significance in mechanical engineering. What are the key differences between static and dynamic equilibrium in mechanical systems? Discuss the fundamental principles behind the operation of simple machines such as levers, pulleys, and inclined planes. How does the conservation of energy apply to mechanical systems, and what are its implications for designing efficient machines?"