The drag force experienced by an object is
- AThe component of resultant fluid dynamics force in the flow direction.Correct
- BThe horizontal force due to pressure variation over the surface of object.
- CThe resultant fluid dynamics force acting on the object.
- DNone of the above
Solution
Concept
Definition of drag force in fluid dynamics
Formula
NONE
Step-by-step solution
1. When a fluid flows past a submerged object, it exerts a total resultant fluid dynamic force on the body surface. 2. The component of this resultant force acting parallel to the direction of fluid flow is defined as the drag force. 3. The component perpendicular to the direction of flow is defined as the lift force. Answer: A
Explanation
When an object moves through a fluid, the surrounding flow exerts a total aerodynamic or hydrodynamic force on its surface. The specific component of this resultant force acting parallel to the direction of relative fluid motion is defined as drag force. Conversely, the component acting perpendicular to the flow direction is known as lift force.
Why the other options are wrong
B) Pressure variation over the surface specifically causes form or pressure drag, rather than the total drag force. C) The resultant fluid dynamics force includes both lift and drag components, not drag alone. D) Option A is correct as drag force is defined as the component of force parallel to the flow direction.
Shortcut
Drag force is always parallel/in the direction of fluid flow, whereas Lift force is perpendicular.
Common mistake
Confusing drag force with total resultant fluid dynamic force rather than its specific component parallel to the flow direction.
Correct answer: A) The component of resultant fluid dynamics force in the flow direction.