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April 20, 2014

April 20, 2014

Posted by **Chong** on Tuesday, November 6, 2012 at 4:16am.

a) How far along the ladder can a 60kg painter climb before the ladder starts to slip?

b) Therefore, at where height above the ground can the same painter climb before the ladder starts to slip ?

- Physics -
**Damon**, Tuesday, November 6, 2012 at 4:55amI am going to say g = 10 m/s^2

base of ladder from wall = 4 m

top of ladder at 4 sqrt 3 = 6.93 m

Take moments about top point of ladder

total weight = 10 (15+60) = 750 N

Friction force = .45*750 = 338 N

Clockwise:

750 N * 4 m = 3000

Counterclockwise:

x is horizontal distance painter to wall

338*6.93 + 150*2 + 600(x)

so

600 x = 3000 - 2342 - 300 = 358

x = .596 m

along ladder to top = 2x = 1.19 m

so along ladder from bottom = 8 -1.19 = 6.8 m from floor along ladder to painter

height of painter = (6.8)/2 sqrt 3 = 5.9 m

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