Final answer:
This physics question involves calculating the angular momentum of a rolling boulder halfway down a hill using energy conservation, and the relationship between linear and angular velocity.
Step-by-step explanation:
The subject of the question is Physics, specifically dealing with the concept of angular momentum. The question asks for the angular momentum of a boulder that is rolling downhill when it is halfway down the hill and at the bottom. To find the angular momentum when it is halfway down, we must first determine the linear speed at that point using energy conservation, then apply the relationship between linear and angular velocity, and finally use the formula for angular momentum of a rolling object.
When the boulder has descended halfway (7.5 m), it has converted half of its potential energy into kinetic energy. This kinetic energy is shared between its linear and rotational motion since it is rolling without slipping. We can calculate the linear speed from the potential energy decrease, then use the known radius to find the angular velocity, and hence the angular momentum, considering the boulder as a solid sphere. However, as this is not a full solution, the actual calculation steps cannot be provided.