Please somebody help me solving these questions

[awaisamin20]

please somebody...i have to submit these questions as assignment on Monday..help me solving these questions that i have posted as attachments..

 

[tiny-tim]

welcome to pf!

hi awaisamin20! welcome to pf!

show us what you've tried, and where you're stuck, and then we'll know how to help!

 

[awaisamin20]

well in question 13(1st picture)...from which point i should calculate the moment??...i tried it with the point B...is it correct??...

 

[tiny-tim]

no!

they mean the moments about the pivot point, O

(that way you don't need to find the reaction force at O, which would be very difficult! )

try again! ​

 

[awaisamin20]

in Question 14...2nd picture...as the tension in the string is equal to the weight...so if we consider every case seprately..each mass causes 'mg' tension in string..so will n no. of masses 'm' cause 'nmg' tension??..

 

[awaisamin20]

no!

they mean the moments about the pivot point, O

(that way you don't need to find the reaction force at O, which would be very difficult! )

try again! ​

which is the pivot point O here??

 

[tiny-tim]

no, stop waffling …

do a proper free body diagram and F_total = 0 equation, for each mass (separately)

 

[pongo38]

For the second diagram with the L shaped member with 10 and Mc on it ... in all fairness, there is a trick to this which involves adding a force at A and then taking it away at the same time, so that the result is unchanged. then you look at the enhanced diagram in a new way.