During rotation only, what direction is the arrow facing?

During rotation only, what direction is the arrow facing?

• A. Straight line opposite
• B. Slightly downwards
• C. Slightly up
• D. Two arrows same direction

Answer: (A)

When something is in pure rotation, the direction of its angular velocity is along the axis of rotation. You determine that direction with the right‑hand rule: curl the fingers in the sense of rotation, and your thumb points along the angular velocity vector. If the rotor is turning by rotation alone, the arrow representing angular velocity would lie straight along the rotation axis, pointing in the opposite direction to the axis side dictated by the rotation sense. In other words, it’s a straight line along the axis, not angled up or down. That’s why the correct choice is a straight line opposite: the arrow shows the axis direction, determined by the rotation direction, with no tilt or tangential component.

When something is in pure rotation, the direction of its angular velocity is along the axis of rotation. You determine that direction with the right‑hand rule: curl the fingers in the sense of rotation, and your thumb points along the angular velocity vector.

If the rotor is turning by rotation alone, the arrow representing angular velocity would lie straight along the rotation axis, pointing in the opposite direction to the axis side dictated by the rotation sense. In other words, it’s a straight line along the axis, not angled up or down.

That’s why the correct choice is a straight line opposite: the arrow shows the axis direction, determined by the rotation direction, with no tilt or tangential component.