Question
A painter weighing 70kg paints the wall of a house, while standing on a uniform wooden plank of length 2m placed on a stand as shown in figure. The mass of the board is 12kg. Find whether the man at the position shown is safe or not.
Solution
The plank tends to turn about A in anticlockwise direction, due to the weight of the painter.
The moment of weight of man about A is,
= 137.2 Nm in anti-clockwise direction.
The plank is uniform, therefore centre of mass of the plank is at the center i.e. at C.
The moment of weight of man about A is,
= 137.2 Nm in anti-clockwise direction.
The plank is uniform, therefore centre of mass of the plank is at the center i.e. at C.
Due to the weight of the plank, the plank tends to turn about A in clockwise direction.
The moment of weight of plank about A is,
= 58.8 Nm, in clockwise direction.
The torque which is acting anticlockwise about A is greater than that in the clockwise direction.
Therefore the plank will turn about O and man will fall.
Thus the man is unsafe.
The moment of weight of plank about A is,
= 58.8 Nm, in clockwise direction.
The torque which is acting anticlockwise about A is greater than that in the clockwise direction.
Therefore the plank will turn about O and man will fall.
Thus the man is unsafe.
