What is the primary cause of drag force on an object moving through a fluid?
A Fluid temperature
B Shape of object
C Object mass
D Object color
The drag force is primarily determined by the shape of the object moving through a fluid. Streamlined shapes experience less drag, while blunt shapes create more turbulence, resulting in higher drag force.
What happens to the velocity profile in a pipe when the flow becomes turbulent?
A Parabolic distribution
B Constant across the pipe
C Flattened with no variation
D Irregular and uneven
In turbulent flow, the velocity profile becomes irregular with fluctuations in velocity across the pipe’s cross‐section. Unlike laminar flow, where the profile is parabolic, turbulent flow exhibits chaotic and uneven distribution.
How does the fluid velocity change when it passes through a constriction in a pipe, assuming constant flow rate?
A Increases
B Decreases
C Stays constant
D Depends on viscosity
According to the continuity equation, when the cross‐sectional area of a pipe decreases, the velocity of the fluid must increase to maintain the same flow rate, assuming the fluid is incompressible.
What is the primary function of boundary layers in fluid flow?
A Increase pressure
B Decrease flow velocity
C Reduce friction
D Increase flow velocity
Boundary layers are thin regions of fluid close to a surface where velocity changes from zero at the surface to free‐stream velocity. They help reduce frictional resistance between the surface and the fluid, lowering drag.
What does the Bernoulli’s equation describe in a flowing fluid?
A Energy conversion
B Pressure variation
C Energy conservation
D Velocity variation
Bernoulli’s equation represents the conservation of mechanical energy in a fluid flow. It relates pressure, velocity, and elevation, stating that the total energy of an incompressible fluid remains constant along a streamline.
What is the role of a pump in a hydraulic system?
A Increase velocity
B Decrease friction
C Measure pressure
D Increase pressure
A pump in a hydraulic system is used to increase the pressure of the fluid, enabling it to flow through the system. This allows the fluid to do work, such as lifting or moving it over a distance.
In which type of flow does the fluid velocity at any point in the flow field not change with time?
A Steady flow
B Turbulent flow
C Laminar flow
D Unsteady flow
Steady flow occurs when the velocity of the fluid at every point in the flow field remains constant over time. This type of flow ensures that the fluid’s characteristics do not vary as the fluid moves.
What is the impact of increasing the pipe diameter on the flow velocity, assuming constant flow rate?
A No effect
B Decreases velocity
C Increases velocity
D Depends on pressure
According to the continuity equation, if the pipe diameter increases, the velocity of the fluid must decrease to maintain a constant flow rate. This inverse relationship ensures that mass flow rate remains constant.
What type of flow is characterized by smooth, parallel fluid motion?
A Turbulent flow
B Unsteady flow
C Laminar flow
D Steady flow
Laminar flow is characterized by smooth, parallel layers of fluid moving in an orderly fashion. There is minimal mixing between layers, and the velocity profile is typically parabolic with the highest velocity at the center.
What is the characteristic of compressible fluid flow?
A No pressure variations
B Constant density
C Density changes significantly
D Constant viscosity
In compressible flow, the fluid density changes significantly with pressure or temperature variations, typically seen in gases. This is different from incompressible flow, where the density remains constant, such as with liquids like water.
What effect does an increase in fluid temperature generally have on viscosity?
A Decreases viscosity
B Increases viscosity
C No effect
D Varies with pressure
For most fluids, an increase in temperature decreases viscosity. As the fluid heats up, the molecules gain more kinetic energy, allowing them to move past one another more easily, reducing internal friction.
What does a high Reynolds number indicate in fluid flow?
A Steady flow
B Laminar flow
C Compressible flow
D Turbulent flow
A high Reynolds number (typically above 4000) indicates that the flow is turbulent. This is characterized by irregular, chaotic motion of fluid, with eddies and vortices, which increases energy loss and drag.
In fluid mechanics, what does the term “drag force” refer to?
A Fluid velocity
B Resistance to motion
C Pressure loss
D Fluid temperature
Drag force is the resistance experienced by an object moving through a fluid. It is primarily affected by the object’s shape, size, and speed, as well as the properties of the fluid through which it moves.
What happens to the pressure in a fluid as it moves upward in a column?
A Increases
B Fluctuates
C Decreases
D Stays constant
In a fluid column, the pressure decreases as the height increases. This is due to the reduction in the weight of the fluid above. The pressure variation is governed by the hydrostatic pressure equation.
What is the result of cavitation in a pump?
A Reduced efficiency
B Fluid vaporization
C Increased pressure
D Increased velocity
Cavitation occurs when local pressure drops below the vapor pressure of the fluid, causing the fluid to vaporize and form bubbles. These bubbles collapse violently when moving to higher-pressure areas, damaging the pump and reducing its efficiency.