The man standing on the ladder in Figure has a mass of 90kg. He climbs up the la
ID: 1822884 • Letter: T
Question
The man standing on the ladder in Figure has a mass of 90kg. He climbs up the ladder and stops at the position shown after he senses that the ladder is just about to slip. The centre of gravity for the man is at G. (Note that where he stops is not half way up the ladder.) If ? = 60? and the wall at B is smooth: (1) Calculate the distances OA and OB. (2) Draw the free body diagram for the ladder showing all applied forces, reactions and frictional forces. Neglect the weight of the ladder (3) Determine the coefficient of static friction at A
Explanation / Answer
sin60*3=OB
==2.598m=OB
OA=3*cos60
OA=1.5m
if man is at x meters from B
x=.9/cos60=1.8m
when ladder is just about to slip =0
take torqe abt point B
1.8*mg*sin150+*mg*3*sin60=mg*3*sin30
=.23
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