S-Video Cable Question?

Force on an elevator by a cable and on a cable by the elevator question?

• (In this problem the elevator is accelerating upward) Is the force exerted by the cable pulling the elevator upward larger, the same, or smaller than the force exerted on the cable by the elevator? Explain your reasoning. My answer: If up is positive acceleration, the force upward must be greater than that of the force downward. The force on the elevator by the cable going up must therefore be larger than the force of the elevator on the cable pulling down. My answer was wrong? Because force is proportional to acceleration, shouldn't the upward force be greater than that of the downward force, therefore creating acceleration?

• Answer:

  Newton's third law- every action has equal and opposite reaction. the force exerted by the cable on the elevator is equal to the force exerted by the elevator on the cable.they act in opposite directions. EDIT : The posittive or negative sign of a force just tells us about the direction of the force.while comparing to forces, the magnitude(numerical value) is important and not the sign(positive or negative)