Question

What is the effect of streamlining on \((a)\) friction drag and \((b)\) pressure drag? Does the total drag acting on a body necessarily decrease as a result of streamlining? Explain.

Short answer

Answer: Streamlining can help reduce both friction and pressure drag on an object. It reduces friction drag by decreasing the surface area in contact with the fluid, and it lowers pressure drag by distributing pressure more evenly around the object. However, streamlining does not always guarantee a decrease in total drag, as the reduction in one type of drag may be offset by an increase in the other type, depending on the specific shape and characteristics of the object.

Step-by-step solution

Define Friction Drag and Pressure Drag

Friction drag is the force that acts parallel to the surface of an object moving through a fluid. It is caused by the friction between the fluid molecules and the object's surface. Pressure drag, on the other hand, is the force that acts perpendicular to the object's surface due to pressure differences around the object.

Discuss the Effects of Streamlining on Friction Drag and Pressure Drag

Streamlining refers to shaping an object so that it can easily flow through a fluid (liquid or gas) with minimal resistance, allowing a smoother flow of the fluid around the object. Streamlining affects friction and pressure drag in the following ways: \((a)\) Friction Drag: Streamlining reduces the surface area of an object in contact with the fluid, thereby reducing the amount of friction between the fluid and the object. This results in a decrease in friction drag. \((b)\) Pressure Drag: A streamlined shape helps distribute the pressure more evenly around the object. This reduces the pressure difference between the front and rear of the object, leading to a lower pressure drag.

Analyze if Streamlining Always Decreases Total Drag

While streamlining does reduce both friction and pressure drag, it doesn't necessarily guarantee that the total drag on a body will always decrease. In some cases, the reduction of one type of drag may be offset by an increase in the other, causing the total drag to remain the same or even increase. For example, if an object's surface becomes more streamlined but its surface area increases, the friction drag may increase, counteracting the benefits of reduced pressure drag. In conclusion, streamlining can help reduce both friction and pressure drag on an object, but it does not always guarantee a decrease in total drag. The total effect of streamlining on drag reduction depends on the specific shape and characteristics of the object in question.