ibrahimahmedolawale
contestada

A uniform pole of 7m long and weighing 10kg is supported by a boy 2m from one end and a man 3m from the other end. At what point must a 20kg weight be attached so that the man would support thrice as much weight as d boy​

Respuesta :

leahxchan

I think it’s :   from left end where x = 0

b up at x = 2.0

10 down at x = 3.5

m up at x = 4.0

20 down at x = x

and

m = 3 b

===================

forces up = forces down

b + m = 10 + 20 = 30

moments clockwise = moments counterclockwise about x = 0

10*3.5 + 20 x = b * 2 + m *4

so

20 x = 2 b + 4 m -35

b + m = 30

m = 3 b

-----------------------------

b + 3 b = 30

b = 30/4 = 15/2 = 7.5

m = 3 b = 22.5

then

20 x = 2 b + 4 m -35

20 x = 15 + 90 - 35 = 70

x = 7/2 = 3.5

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