a 9m cable has to hold 9000 kg . the steel to be used has failure stress of 1200MNm_2. Force=9000kg*10ms_2. what is diameter of the cable?
Assume that the weight of the cable is negligable, then the force exerted by the cable is $\displaystyle 9000 g$ Newtons.
Let the diameter of the cable be $\displaystyle d$ metres, then the crossectional area of the cable is $\displaystyle \pi d^2/4$.
Therefore the stress is:
$\displaystyle \frac{9000 g}{\pi d^2/4} < 1200 \times 10^6$ $\displaystyle N/m^2$
CB