Static force equilibrium problem involving simply pully syst

[J-dizzal]

Homework Statement

A former student of mechanics wishes to weigh himself but has access only to a scale A with capacity limited to 120 lbs and a small 20-lb spring dynamometer B. With the rig shown he discovers that when he exerts a pull on the rope so that B registers 19 lb, the scale A reads 96 lb. What is his correct weight?
[/B]
http://edugen.wileyplus.com/edugen/courses/crs7925/art/qb/EAT_1314936802947_0_5416955130664096.jpg

Homework Equations

ΣF=0

The Attempt at a Solution

 

[Dr. Courtney]

Take more care to only add all the forces acting on an object. If a weight is only acting through a tension, then you add only the tension not the weight too.

 

[J-dizzal]

Take more care to only add all the forces acting on an object. If a weight is only acting through a tension, then you add only the tension not the weight too.

yes of course. ΣF_y= -19-96+4T_B-T_A=0 thanks Dr

 

[SammyS]

Homework Statement

A former student of mechanics wishes to weigh himself but has access only to a scale A with capacity limited to 120 lbs and a small 20-lb spring dynamometer B. With the rig shown he discovers that when he exerts a pull on the rope so that B registers 19 lb, the scale A reads 96 lb. What is his correct weight?
[/B]
http://edugen.wileyplus.com/edugen/courses/crs7925/art/qb/EAT_1314936802947_0_5416955130664096.jpg

Homework Equations

ΣF=0

The Attempt at a Solution

[ IMG]http://i1164.photobucket.com/albums/q562/falsovero/20150703_115323_zpsnkhqktuf.jpg[/PLAIN]

Unfortunately, we can't open that link from Wiley without a username/password.