Question

In Figure P12.59, an 80 kg construction worker sits down 2.0 m from the end of a 1450 kg
steel beam to eat his lunch. What is the tension in the cable?

Short answer

The tension in the cable is 1.53 x 10⁴ N

Step-by-step solution

Given Information

Mass of worker = 80 kg

worker sits 2.0 m from the end

Mass of steel beam = 1450 kg

Explanation

First draw the diagram as below to understand and solve the problem

And then equate the clockwise and anti-clock wise torque about the origin

We, get

$W_b\times 3m+W_w\times 4m=Tsin30°\times 6m$

Substitute the given value and solve for T

use weight as mg .. so multiply mass with g.

$$\begin{gathered} \mathrm{T}=\frac{\left(1450\mathrm{kg}\times 9.8\mathrm{m}/{\mathrm{s}}^2\times 3m\right)+\left(80\mathrm{kg}\times 9.8\mathrm{m}/{\mathrm{s}}^2\times 4\mathrm{m}\right)}{6m\times \sin 30°} \\ \mathrm{T}=15,255.3333\mathrm{N} \\ \mathrm{T}=1.525\times {10}^4\mathrm{N} \end{gathered}$$