2 A uniform plank, of length 6 metres, has mass 40 kg . The plank is held in equilibrium in a horizontal position by two vertical ropes attached to the plank at \(A\) and \(B\), as shown in the diagram.
\includegraphics[max width=\textwidth, alt={}, center]{03994596-21ad-4201-8d64-ba2d7b7e0a77-2_323_1162_1464_440}

1. Draw a diagram to show the forces acting on the plank.
2. Show that the tension in the rope attached to the plank at \(B\) is \(21 g \mathrm {~N}\).
3. Find the tension in the rope that is attached to the plank at \(A\).
4. State where in your solution you have used the fact that the plank is uniform.