-A uniform 600 kg beam,6 m long,is freely pivoted at P.The beam is supported in a horizontal position by a light strut,5 m long,which is freely pivoted at Q and is loosely pinned to the beam at R.A load of mass is suspended from the end of the beam at S.A maximum compression of 25,000 N in the strut is permitted,due to safety.In the figure,under maximum load the y-component of the force exerted on the beam by the pivot at P is closest to:
A)7060 N
B)4560 N
C)9560 N
D)10,000 N
E)zero

Question

-A uniform 600 kg beam,6 m long,is freely pivoted at P.The beam is supported in a horizontal position by a light strut,5 m long,which is freely pivoted at Q and is loosely pinned to the beam at R.A load of mass is suspended from the end of the beam at S.A maximum compression of 25,000 N in the strut is permitted,due to safety.In the figure,under maximum load the y-component of the force exerted on the beam by the pivot at P is closest to:
A)7060 N 
B)4560 N 
C)9560 N 
D)10,000 N 
E)zero

Quizplus · Accepted Answer

The maximum compression in the strut is 25,000 N. The strut is 5 m long and the beam is 6 m long. Therefore, the moment of the force exerted by the strut about the pivot at P is 25,000 N * 5 m = 125,000 Nm. The moment of the force exerted by the load about the pivot at P is 10,000 N * 6 m = 60,000 Nm. Therefore, the y-component of the force exerted on the beam by the pivot at P is (125,000 Nm - 60,000 Nm) / 6 m = 7060 N.

-A Uniform 600 Kg Beam,6 M Long,is Freely Pivoted at P.The