Final answer:
The student's questions are related to physics, focusing on the deformation of materials and rotational dynamics. Calculations are performed using the shear modulus to determine deformation in materials and integrating mass distribution to find the moment of inertia for rotational systems.
Step-by-step explanation:
The student's question pertains to mechanics, a branch of physics that deals with forces and their effects on the motion of objects. Specifically, the questions seem to revolve around static equilibrium and rotational dynamics, such as calculating changes in dimensions due to applied forces and determining the moment of inertia of different objects. A crucial concept here is the shear modulus, which measures the rigidity of a material and helps in calculating deformation.
For the specific question regarding the steel rod, we need to apply Hooke's Law for elongation of materials to find the required diameter. Given the weight of the truck, we can calculate the force exerted on the rod, which corresponds to the stress. The elongation of the rod can be related to the stress through Young's modulus (not the shear modulus). Therefore, we can establish the equation that relates these quantities and solve for the necessary diameter of the steel rod.
In the rotational dynamics part, the moment of inertia is calculated for systems involving a rod and masses attached. This involves integrating over the distribution of mass using calculus, given the linear density of the rod.