Question 6
If the line of action of a force passes straight through the axis of rotation, what does that force do to the body?
The right answer is the one marked above.
The moment is zero, so it does not turn. The perpendicular distance is zero, and force × 0 = 0. However large the force, there is no turning effect.
A large force does not always give a large moment. If the distance is zero so is the product — try opening a door by pushing exactly on its hinge and you will feel it.