Final answer:
The internal force has a greater mechanical advantage over the external force when the internal moment arm is greater than the external moment arm.
Step-by-step explanation:
The internal force (muscle force) has a greater mechanical advantage over the external force when the internal moment arm is greater than the external moment arm. The mechanical advantage is the ratio of the forces exiting and entering the machine, and by increasing the lever arm of the internal force, the size of the force is increased. This means that the internal force can exert more torque and have a greater mechanical advantage.