MHB Mechanics- connected particles

[Shah 72]

A horizontal bar of mass 1kg hangs from a pair of parallel vertical rods of negligible mass, attached to either end of the bar. A third vertical rod is connected to the middle of the bar and a 4kg mass hangs from this below the rod. Work out the tension in each of the rods.
I got the tension in the third vertical rod= 40N. I don't know how to find the tension of the other two rods.

 

[skeeter]

did you sketch a FBD?

forces acting on the 1 kg bar …

$T_1+T_2$ up, $1g + T_3$ down

 

[Shah 72]

did you sketch a FBD?

forces acting on the 1 kg bar …

$T_1+T_2$ up, $1g + T_3$ down

T1+T2=50N, T3=40N

 

[skeeter]

T1+T2=50N, T3=40N

so …

$T_1 =$ ?

$T_2 =$ ?

… and why?

 

[Shah 72]

so …

$T_1 =$ ?

$T_2 =$ ?

… and why?

T1=T2 = 25 as T3 is at the midpoint of the horizontal bar

 

[skeeter]

yes, but that’s not the “physics” reason … what do you know about translational and rotational equilibrium?

recommend you look them up if you haven’t heard those terms before

 

[Shah 72]

yes, but that’s not the “physics” reason … what do you know about translational and rotational equilibrium?

recommend you look them up if you haven’t heard those terms before

Sure. Thanks!