Turning effect of forces - moments

[INeedHelpPls]

Homework Statement

A uniform board is hinged at A and supported by a vertical rope at P, 6.0m from A. A man of weight 700N stands at the end of the board at point B, which is 15.0m from hinge A. If weight of board is 50N,calculate the tension T in the rope.

Homework Equations

By principle of moments and taking moments about the hinge A, sum of ACW moments= sum of CW moments

The Attempt at a Solution

By principle of moments and taking moments about hinge A,
sum of ACW moments = sum of CW moments
700 x 15 = T x 6
T= 1750N

however, final answer is 1812.5N, can anyone help please? Thanks in advance!

 

[ehild]

The Attempt at a Solution

By principle of moments and taking moments about hinge A,
sum of ACW moments = sum of CW moments
700 x 15 = T x 6
T= 1750N

however, final answer is 1812.5N, can anyone help please? Thanks in advance!

You forgot the weight of the board.

ehild

 

[sigmaro]

i could not understand what you meant by ACW and CW but this question is not that hard, just take all moments about A, it must be equal to 0 since there is a static equilibrium.
taking upwards +, downwards -
6T-50.7,5-700.15=0
T=(10875)/6=1812.5N

 

[sigmaro]

Sorry ehild, while i was typing there was no answer

 

[INeedHelpPls]

okay thanks alot.. but i don't understand sigmaro's working :(
ACW= anti-clockwise and CW =clockwise.. something like taking upwards as + and downwards as -

 

[sigmaro]

it is nothing but rearranging
ACW=CW as ACW-CW=0 or CW-ACW=0
later on you will see that moment is a vector in fact and you will get used to this notation

 

[INeedHelpPls]

what does the comma mean?

 

[sigmaro]

i used "." instead of "*", and so i used "," instead of "."
7,5=15/2