QUESTION (see attached image file):

enter image description here

I got stuck when trying to find tension for part A; see my working below. and help me solve.

enter image description here


2 Answers 2


It looks like you're grasped the basic concept of the question -- using trigonometry to solve for the inclination of the cable, and then summing moments about point C to find the tension in the cable.

From the trig, angle alpha is 47.6025 degrees (as shown in sketch below).


Then, summing moments about point C, the tension T is calculated.

Summation of Moments

  • $\begingroup$ This is also accepted answer. Good job :) $\endgroup$
    – Jem Eripol
    Sep 11, 2017 at 23:56

See image for reference.

The problem is a trigonometric problem. The trick is for you to solve the value of A, B, C, and x.

To solve for x, you'll need the cosine law such that:

Angle C is very obvious to be equal to 70 degrees.

$$x^2 = 10^2 + 12^2 - 2(10)(12)cos(70)$$

$$x = 12.7246 \ cm\ = 12.72 cm.$$

now, solve for the value of angle (A+B). Angle A is equal to 20 degrees.

$$cos (A+B) = (12^2 - 10^2 - 12.72^2) / (-2*10*12.72)$$

therefore, $$(A+B) = 62.416\ degrees$$

Rotated image.

Now, rotating the FBD by 20 degrees clockwise will give the image above. Summing up moments along the hinge (C) will give:

$$T sin(62.416) * 10 = 200 sin (70) * 15$$

$$T = 318.06 \ N \ ---->answer$$


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.