A 450.0 N, uniform, 1.50 m bar is suspended horizontally by two vertical cables at each end. Cable A can support a maximum tension of 550.0 N without breaking, and cable B can support up to 300.0 N. You want to place a small weight on this bar.
1)What is the heaviest weight you can put on without breaking either cable?
2)Where should you put this weight?

Respuesta :

Answer:

1) [tex] W_{object} = 400 N [/tex]

2) x = 0.28 m from cable A.

Explanation:

1 ) Let's use the first Newton to find the , because bar is in equilibrium.

[tex] \sum F_{Tot} = 0 [/tex]

In this case we just have y-direction forces.

[tex] \sum F_{Tot} = T_{A}+T_{B}-W_{bar}-W_{object} = 0 [/tex]

Now, let's solve the equation for W(object).

[tex]  W_{object} = T_{A}+T_{B}-W_{bar} = 550 +300 - 450 = 400 N [/tex]

2 ) To find the position of the heaviest weight we need to use the torque definition.

[tex] \sum \tau = 0 [/tex]

The total torque is evaluated in the axes of the object.

Let's put the heaviest weight in a x distance from the cable A. We will call this point P for instance.

First let's find the positions from each force to the P point.

[tex] L = 1.50 m [/tex]  ; total length of the bar.

[tex] D_{AP} = x [/tex]  ; distance between Tension A and P point.

[tex] D_{BP} = L-x [/tex] ; distance between Tension B and P point.

[tex] D_{W_{bar}P} = \frac{L}{2}-x [/tex] ; distance between weight of the bar (middle of the bar) and P point.

Now, let's find the total torque in P point, assuming counterclockwise rotation as positive.

[tex] \sum \tau = T_{B}(L-x)-T_{A}(x)-W_{bar}(\frac{L}{2}-x) = 0 [/tex]

Finally we just need to solve it for x.

[tex] x = \frac{T_{B}L-W_{bar}(L/2)}{T_{B}+W_{bar}+T_{A}} [/tex]

[tex] x = 0.28 m [/tex]

So the distance is x = 0.28 m from cable A.

Hope it helps!

Have a nice day! :)

Answer:

Weight = 400 N

d = 0.28m

Explanation:

∑Fy = 0 gives Ta + Tb - W - Wbar = 0.

W=Ta + Tb - Wbar = 550N + 300N - 450N = 400N

To find distance you need to use the net torque formula.

∑τ = 0 gives Tb(d) - W * d - Wbar * ([tex]\frac{d}{2}[/tex])

τ = Force * distance

d = [tex]\frac{Tb*(1.5) - Wbar(0.75)}{W}[/tex]

d = 0.28m