Final answer:
The tension in the cord is zero when a heavy steel ball suspended from a block of wood is dropped through the air in freefall, neglecting air resistance, because the system is not resisting any motion and both parts are accelerating due to gravity alone.
Step-by-step explanation:
The question asks about the tension in the cord when a heavy steel ball B, suspended from a block of wood W, is dropped through the air, neglecting air resistance. When the entire system is in freefall, both the ball and the block of wood are accelerating downward at the same rate, which is the acceleration due to gravity (g). According to Newton's laws, specifically the second law, the net force is the mass times the acceleration of the object. However, since both the ball and the block are in freefall, there is no net force acting on the ball in the frame of reference of the falling system, meaning there is no tension in the cord. Therefore, the correct answer is c. Zero.
It is important to recognize that under different circumstances, such as when an object is stationary or when there is an acceleration different from that of gravity, the tension would be equivalent to the weight of the supported mass or modified by the additional forces acting on the system. However, in this case of freefall with no air resistance, the tension is zero because the system is not resisting any motion; both the ball and the block are moving together due to gravity alone.