The Cable Has A Tension If The Acrobat Falls

Find T, the tension in the cable in kilo-Newtons. Take g to be 9.8 m / s 2 9.8~m/s^2 .


The answer is 29.4.

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6 solutions

Tunk-Fey Ariawan
Mar 3, 2014

Assuming the system at equilibrium state, then by applying Newton's first law on the vertical axis, we obtain F = 0 2 T sin θ m g = 0 2 T 75 7 5 2 + 9 , 00 0 2 = m g T = m g 2 7 5 2 + 9 , 00 0 2 75 = 50 9.8 2 7 5 2 + 9 , 00 0 2 75 29 , 401.021 N = 29.401021 k N \begin{aligned} \sum F&=0\\ 2T\sin\theta-mg&=0\\ 2T\frac{75}{\sqrt{75^2+9,000^2}}&=mg\\ T&=\frac{mg}{2}\cdot\frac{\sqrt{75^2+9,000^2}}{75}\\ &=\frac{50\cdot9.8}{2}\cdot\frac{\sqrt{75^2+9,000^2}}{75}\\ &\approx29,401.021\;N\\ &=\boxed{29.401021\;kN} \end{aligned}


# Q . E . D . # \text{\# }\mathbb{Q.E.D.}\text{ \#}

why did u use sin?

Alfredo Ryelcius - 7 years, 3 months ago

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Allfredo : it'ss depend on your asumption about the angle on free body diagram

Yudi Prabudi - 7 years ago

did it using .075 m and 9 m.....and thought i was wrong

Vaibhav Bhasin - 7 years, 2 months ago
Arijit Banerjee
Mar 18, 2014

break the tension into its two components. The cos term cancels each other while 2T sin (theta) = mg.. now since sin (theta ) almost = theta .... 2T theta = 50 * 9.8 . on solving T = 29.4

nice solution!

Sudipan Mallick - 7 years, 2 months ago

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Thanks bhai.. :P

Arijit Banerjee - 7 years, 2 months ago
Long Phạm Sơn
Feb 25, 2014

Assume that the acrobat is standing steadily on the rope(or sth you name it). so we have : T1 + T2 + P = 0 (all are vectors) since T1=T2 then T1 = T2 = 1/2P=P1 (all vectors) now we need to calculate the angle between the T1 and P1 . using cosine you can get the angle is aprrox 89.5225 degree. now we have P1/T1 = cosA <=> 1/2P /T1 = cosA <=> 1/2mg / T1 = cos(89.5225) =>Solve for T1 .(sorry for bad English and not having the diagram)

just slipped to divide by 2

Yash Jaiswal - 7 years, 3 months ago
Jaivir Singh
Apr 18, 2014

2T*(75 x 10 to the power -3 / 3) = 50 x 9.8

Laxman Selvam
Mar 19, 2014

In equilibrium, the horizontal components cancel out each other. the net upward force is equal to the net downward force hence Tension = (Mg)/(2 cosx)....cosx = 0.075/9 T= 29.4 KN

Rahasut Khajuwia
Mar 11, 2014

1 Take 7.5mm as 7.5E-2 m 2. Distribute the force of its weight on both the strings so you would get 245N. 3. Make FBD of it and equate 245 with Tsin 4. You can write sinangle as 7.5E-2/9 and then equate it so it would be app. 29.4.

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