For a body moving through a fluid, Skin Friction Drag is primarily caused by
- AThe shear stresses exerted by the fluid on the surface of the body.Correct
- BThe pressure difference between the front and rear of the body.
- CThe formation of a wake behind the body.
- DThe weight of the body acting downwards.
Solution
Concept
Skin Friction Drag
Step-by-step solution
1. Review the given question regarding the primary cause of skin friction drag on a body moving through a fluid. 2. Recall that skin friction drag arises directly from fluid viscosity creating shear stresses along the contact surface of the body. 3. Compare this with the given options and select Option (a) as the correct choice.
Explanation
Skin friction drag is caused by the friction between the surface of a moving object and the fluid surrounding it. As the fluid rubs against the object's outer surface, viscosity generates shear stresses that resist the movement of the object.
Shortcut
To easily remember Skin Friction Drag vs. Pressure Drag, use this simple memory trick: - Skin Friction Drag = Surface Shear: Rubbing against the "skin" or surface of the object creates viscous shear stresses. - Pressure (Form) Drag = Shape & Wake: Caused by the overall shape of the body and pressure difference between front and rear.
Common mistake
A common mistake is selecting option B by confusing skin friction drag with form (pressure) drag. Pressure drag is caused by the pressure difference between the front and rear of a body and wake formation, whereas skin friction drag is directly caused by viscous shear stresses along the body's surface.
Correct answer: A) The shear stresses exerted by the fluid on the surface of the body.