Physics Question

Question

A heavy concrete panel is being lifted into position in a building by means of a crane (see figure below). The tension of 1.70  10⁴ N in the supporting cable produces a torque with respect to point O. (Let L = 17.3 m.)

(b) Find the torque.

Answer 1

The problem involves finding the component of T that does the torquing and then calculating the torque. If you break T into a component perpendicular to the beam and one parallel to the beam, you can see that the one parallel to the beam contributes no torque. The formula for torque is torque = LTsinθ, where L is the length of the beam, T is the tension and θ is the angle between L and T in this case 53 degrees. Looking at the formula if we look at Tsinθ we see that it is the component perpendicular to the beam as explained above. Now all you have to do is plug in numbers and get the answer. Note that this is the torque about an axis through O as shown in the figure. This is an axis perpendicular to the plane of the page and is is a vector.