View Full Version : Physics: Torques
 
 Echo901
Nov 6, 2013, 06:50 PM
A 1350-N uniform boom at phi = 64.5° to the horizontal is supported by a cable at an angle θ = 25.5° to the horizontal as shown in the figure below. The boom is pivoted at the bottom, and an object of weight w = 1850 N hangs from its top. 
Here is a link for the diagram:  http://www.webassign.net/sercp9/8-p-028.gif
 
Find the tension in the support cable (kN)
Find the components of the reaction force exerted by the pivot on the boom. (kN)
 ebaines
Nov 7, 2013, 06:31 AM
Hint: start by using sum of moments about the pivot point to find tension in the cable.  The rest is then using sum of forces in the x- and y-directions equal 0.
 Echo901
Nov 7, 2013, 05:34 PM
Hint: start by using sum of moments about the pivot point to find tension in the cable.  The rest is then using sum of forces in the x- and y-directions equal 0.
 
so I found the tension in the cable to be 1.45kN
and using the following equation I found Fy to be 2.58kN
Fy(Beam)+Fy(weight)-F(tension)*sin25.5
 
But now I am a little confused as to how to set up the equation to get Fx. I know that Fx=0 and the components that make up Fx are the x components of the beam, the weight and the tension in the cable, but I don't really know how to approach setting up the equation, and I am unsure of which angle to use as well.
 ebaines
Nov 8, 2013, 06:58 AM
The x-component of the weight and the boom are both zero, because the force of gravity is straight down (in the y-direction only)  So you have:
 
 \sum F_x = 0 = F_x(pivot)  - F(tension) \cos(25.5)
 Echo901
Nov 8, 2013, 07:52 AM
Thank you so much!