Question

Vector forces of equal magnitude but in the opposite direction and with moment arms of the same distance are most likely to have what effect on joint movement?

A. Movement of the joint in the direction of the muscle force
B. No movement of the joint
C. Movement of the joint in the direction of the force opposing the muscle
D. Alternating movement of the joint in each direction of the forces

Answer 1

Forces of equal magnitude in opposite directions with the same moment arm length on a joint will likely result in no movement of the joint due to static equilibrium.

Step-by-step explanation:

When vector forces of equal magnitude but in opposite directions act on a joint with moment arms of the same distance, they create a situation of static equilibrium. This means there is no net movement of the joint because the forces cancel each other out. Since muscles can only contract and cannot actively extend, pairs of muscles work in opposition to move joints. A pair includes a flexor, which contracts to bend a joint, and an extensor, which contracts to straighten it. When the muscle force and the force opposing the muscle are equal and opposite, their effects on joint movement negate each other, resulting in no movement or a balanced state.