A 2.0-m-long, 25-kg ladder is resting against a house wall, making a 21 angle wi

Question

A 2.0-m-long, 25-kg ladder is resting against a house wall, making a 21 angle with the vertical wall. The coefficient of static friction between the top of the ladder and the wall the coefficient is 0.00. a). Determine the minimal coefficient of static friction between the ladder feet and the ground needed for the ladder to stay in rest. b).Determine the magnitude of the normal force of the wall on the ladder. c). Determine the magnitude of the normal force of the floor surface on the ladder. d). Determine the magnitude of the force of friction between the floor and the ladder.

Explanation / Answer

a] Let Normal by wall N1,

Balancing torque about foot of the ladder.

mgL/2 sin 23 degree = N1*cos 23 degree L

N1 = mg/2 tan 23 degree

friction = uN2 = u*mg

also by force balance, umg = mg/2 tan 23 degree

u = 0.5*tan 23 degree = 0.2122

b] Normal N1 = mg/2 tan 23 degree = 0.2122*25*9.8 = 52 N

c] N2 = mg = 245 N

d] friction = N1 = 52N

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