how did the physical models make it difficult to show what happens to the plates and mantle at plate boundaries?

Physical models made it difficult to show what happens to the plates and mantle at plate boundaries because they did not accurately represent the mantle or the complex processes occurring at these boundaries. These models struggled to simulate the bending, breaking, and interactions of rigid crustal plates, especially how they behave at subduction zones where one plate sinks into the mantle. The physical models often oversimplified the mantle and plate mechanics, making it challenging to depict the detailed dynamics that truly happen at plate boundaries such as slab pull, bending of plates, and mantle convection processes.