The normal stress across the principal plane is known as
- AShear stress
- BMaximum shear stress
- CPrincipal stressCorrect
- DTangential stress
Solution
Concept
A principal plane has zero shear stress, and the normal stress on it is called principal stress.
Step-by-step solution
1. A principal plane is a plane on which shear stress is zero. 2. Only normal stress acts on this plane. 3. This normal stress is called principal stress. 4. So the answer is (C).
Explanation
On a principal plane, shear stress is zero. The only stress acting there is normal stress, and we call it principal stress. Principal stresses are the maximum and minimum normal stresses at a point.
Why the other options are wrong
A: Shear stress is zero on a principal plane. B: Maximum shear stress acts on planes at 45° to the principal planes, not on the principal planes. D: Tangential stress is another name for shear stress, which is zero on a principal plane.
Shortcut
Principal plane means zero shear, so the stress on it is the principal (normal) stress.
Common mistake
Students confuse principal planes with the planes of maximum shear stress.
Correct answer: C) Principal stress