# Fluid Mechanics Questions and Answers – Types of Forces Acting in Moving Fluid

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This set of Fluid Mechanics Multiple Choice Questions & Answers (MCQs) focuses on “Types of Forces Acting in Moving Fluid”.

1. Which among the following force is developed due to resistance of a fluid flow?
a) Viscous force
b) Inertial force
c) Gravity force
d) Pressure force

Explanation: Viscous force is the force that is developed due to resistance of a fluid flow. Viscous force is equal to the product of shear stress due to viscosity and surface area of the fluid. It acts in the opposite direction to that of the acceleration.

2. Which among the following force is developed due to resistance in its state of motion?
a) Viscous force
b) Inertial force
c) Gravity force
d) Pressure force

Explanation: Inertial force is the force that has resistance to any physical object that undergoes a change in its state of motion. Inertial force is the product acceleration of fluid and its mass. It acts opposite to the direction of acceleration.

3. Which among the following is the correct formula for gravitational force?
a) F= Gm1m2/r2
b) F= Gm1m2
c) F= m1m2/r2
d) F= Gm1m2/r3

Explanation: Gravitational force was derived by Newton’s theory of gravitation. It is defined as the product of mass and acceleration due to gravity of the fluid flow. It is mainly present in cases of open surface fluid flow.

4. Which among the following is present in pipe flow?
a) Viscous force
b) Inertial force
c) Gravity force
d) Pressure force

Explanation: Pressure is a force that is applied perpendicular to the surface of an object over a unit area of force. It is defined as the product of pressure intensity and cross-sectional area of the flowing fluid. Pressure force is present in case of pipe flow.

5. A force that is caused due to attraction of particles in the layer of fluid bulk is called?
a) Viscous force
b) Inertial force
c) Surface tension force
d) Pressure force

Explanation: Surface tension is caused due to the attraction of particles in the surface layer of the fluid in bulk quantities. Surface tension force is defined as the product of surface tension and length of flowing fluid.

6. A force that is needed to bring back the body to its original position is called as?
a) Viscous force
b) Elastic force
c) Gravity force
d) Pressure force

Explanation: Elastic force is the force that brings a body back to its original position. It is defined as the product of elastic stress and the area of the flowing fluid.

7. How do we measure the flow rate of liquid?
a) Coriolis method
c) Conveyor method
d) Ionization method

Explanation: Coriolis concept of measurement of fluid takes place through the rotation with the reference frame. It is an application of the Newton’s Law. The device continuously records, regulates and feeds large volume of bulk materials.

8. The three major fluid forces are Buoyancy, drag and lift.
a) True
b) False

Explanation: Buoyancy, drag and lift are the three major fluid forces. These forces have significant importance in various applications. For example: Shotput, badminton, cricket, baseball, cycling, swimming etc.

9. The drag force acts in _____ to the flow velocity.
a) Perpendicular direction
b) Same direction
c) Opposite direction
d) Different directions

Explanation: The drag force acts in the opposite direction to that of the relative flow velocity. It acts in the opposite direction with respect to a surrounding fluid flow. Thus, option Opposite direction is correct.

10. Drag force is affected by__________
a) Cross sectional area and smoothness
b) Rigidity and density
c) Pressure and temperature
d) Mass

Explanation: Drag force is affected by cross sectional area and smoothness. If it is affected by cross sectional area, then it is called form drag. If it is affected by surface smoothness, then it is called as surface drag.

11. The lift force acts in _____ to the flow velocity.
a) Perpendicular direction
b) Same direction
c) Opposite direction
d) Different directions

Explanation: The lift force acts in the perpendicular direction to that of the relative flow velocity. It acts in the perpendicular direction with respect to a surrounding fluid flow. Thus, option Perpendicular direction is correct.

12. Which among the following is the correct formula for drag?
a) D = Cd * A * 0.5 * r * V2
b) D = Cd * A * 0.5 * r * V*2
c) D = Cd * A * 0.5 * r * V/2
d) D = 0.5 * r * V

Explanation: The drag force acts in the opposite direction to that of the relative flow velocity. It acts in the opposite direction with respect to a surrounding fluid flow. Thus, the correct option is D = Cd * A * 0.5 * r * V2.

13. Which among the following is the correct formula for lift?
a) D = Cl * A * 0.5 * r * V2
b) D = Cl * A * 0.5 * r * V*2
c) D = Cl * A * 0.5 * r * V/2
d) D = 0.5 * r * V

Explanation: The lift force is a force that acts in the perpendicular direction to that of the relative flow velocity. It acts in the perpendicular direction with respect to a surrounding fluid flow. Thus, the correct option is D = Cl * A * 0.5 * r * V2.

Sanfoundry Global Education & Learning Series – Fluid Mechanics.

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