Question

A scaffold of mass 40 kg and length 4.5 m is supported in a horizontal position by one vertical cable at each end. A window washer of mass 86 kg stands at a point 1.1 m from one end. What is the tension in the cable?

Answer 1

`R_A=402.018\ N`

`R_B=832.782\ N`

Step-by-step explanation:

Given:

• mass of scaffold,
  `m_s=40\ kg`

• length of scaffold,
  `l=4.5\ m`

• point mass of window washer,
  `m=86\ kg`

• distance of point mass from one end,
  `d=1.1\ m`

Here we consider the mass of the beam as uniformly distributed load concentrated at mid-span.

Using the schematic diagram:

Balancing forces:

`\sum F=0`

`R_A+R_B=(40+86)* 9.8` ..............................(1)

Balancing moment about point A:

`\sum M_A=0`

`4.5* R_B=9.8* (86* 3.4+40* (4.5)/(2))`

`R_B=832.782\ N` ......................................(2)

Putting value from eq. (2) into eq. (1)

`R_A+832.782=1234.8\ N`

`R_A=402.018\ N`