Solution :
Given : Mass of ladder = 10 kg
Length of ladder = 5 m
Weight of window cleaner = 75 kg
a). Now equate the torque about the lowermost point of the ladder is given by :
Here, N = normal force that the glass exerts on the ladder
Therefore,
= 280 N (in 2 significant figures)
b). Equate the forces along horizontal direction,
The horizontal component of the friction,
The vertical component of the friction,
= 833 N
Therefore, the net frictional force,
= 879.7 N
= 880 N (in 2 significant figures)
c). The angle the forces makes
Therefore in 2 significant figures =