Question

A uniform steel girder of weight 22KN and of length 12m is lifted off the ground at one end by means of a crane. When the raised end is 2.0m above the ground, the cable is vertical.
A. Sketch a free-body diagram of the girder in this position
b. Calculate the tension in the cable at this position and the force of the girder on the ground

Answer 1

Answer:

Explanation:

For free body diagram see attached sheet .

W is weight of steel girder acting at the middle point of its length . T is tension in the cable .

OB = √ ( 12² - 2² )

= 11.83 m .

OC = 11.83 / 2 = 5.915 m

Taking moment of tension T and weight W about point O

W x OC = T x OB

22 x 5.915 = T x 11.83

T = 22 x 5.915 / 11.83

= 11 kN

Considering forces acting in vertical direction and equating forces in opposite direction

T + R = W

R = W - T

= 22 - 11 = 11 KN

So force of grinder on the ground = R

= 11 KN.