12) An elephant is stopped by a rope wound twice around the rough trunk of a tree. If the elephant exerts a pull of 1000 kgf, the minimum force required to stop the elephant is (Coefficient of friction between the rope and the tree is 0.3)
Answer is:
23 kgf
Related ISRO Technical Assistant Mechanical Question Paper - 2017 with Answer Key
Answer is:
Planes which have no shear stress
Explanation:
Principal Stresses and Strains: It has been observed that at any point in a strained material, there are three planes, mutually perpendicular to each other, which carry direct stresses only, and no shear stresses.
A little consideration will show that out of these three direct stresses, one will be maximum, the other minimum and the third an intermediate between the two. These particular planes, which have no shear stress, are known as principal planes. The magnitude of direct stress, across a principal plane, is known as principal stress.