Final answer:
The question involves complex high school-level physics problems dealing with forces, tension, and Newton's laws of motion in different scenarios such as lifting blocks, tensions in strings, and connected mass systems.
Step-by-step explanation:
The student's question relates to physics concepts such as forces, tension, and mechanical energy. It appears to deal with several physics problems: the dynamics of a block being lifted and placed on a shelf, the tension in a string with hanging objects, and calculating the resultant forces in a system of masses connected by ropes. These types of problems require an understanding of Newton's laws of motion, principles of statics and dynamics, and energy conservation.
For instance, to solve for the tension in ropes or strings supporting weights, one must consider the forces acting on each segment of the string and apply Newton's second law, F=ma, where F is the force applied, m is the mass, and a is the acceleration. Similarly, when considering the motion of blocks connected by a rope, one must account for gravitational forces, tension in the rope, acceleration, and in some cases, friction.