Figure 2 shows a decorator's plank, which is 5 m in length, supported on two trestles. The mass of the plank is 37 kg and the mass of the decorator is 70 kg.
In order to paint a stairwell the decorator has to position themselves at point A, as shown on Figure 2. To stop the plank tipping, the decorator's assistant attaches weights to a rope at point B.

Draw a diagram showing all the forces acting on the plank and the distances from point B that each force acts. State, in words, two conditions that must be
satisfied for the plank to be stationary and stable.
For each of the two conditions you have identified in part (b), using the information contained in your diagram. write an equation that must be satisfied for the bar to remain stationary. Do not include units in your equations.

 

  

1.5 m 2 m 1 m Figure 2 The decorator's plank