Sample Problems Based on Fluid Friction

Question 1: Boats and airplanes are made in streamlined shape. Why?

Answer: 

A shape which is wide in middle and tapered at ends is called a streamlined shape. Such a shape reduces drag or fluid friction. 

Hence, a streamlined body can easily move through a fluid. Birds and fish are naturally endowed with streamlined body. Boats and airplanes are also made streamlined so that they can easily move through air or water.

Question 2: Why are the bodies of boats, planes, cars, etc. streamlined?

Answer:

For objects that move in fluids such as boats, planes, cars, etc.

The shape of their body is streamlined in order to reduce the friction between the bodies of the objects as the fluid.

Question 3: How can we land smoothly using a parachute with the help of Viscous drag?

Answer: 

When a parachute is just opened, the velocity is down and the acceleration is up. Your speed decreases as a result, which is the whole point behind the parachute.

Speed decreases, so drag decreases. Drag decreases, so the net force decreases.

Question 4: What are the advantages of a streamlined body?

Answer: 

Streamlining your body reduces the friction of movement to a minimum thus decreasing overall drag.

For fishes having a streamlined body that is smooth helps save energy it would otherwise have to expand swimming.

Question 5: What is laminar flow?

Answer: 

Laminar flow, type of fluid (gas or liquid) flow in which the fluid travels smoothly or in regular paths, in contrast to turbulent flow, in which the fluid undergoes irregular Fluctuations and mixing.

Question 6: Which of the following statements is incorrect?

(a) Friction acts on a ball rolling along the ground

(b) Friction acts on a boat moving on water

(c) Friction acts on a bicycle moving on a smooth road

(d) Friction does not act on a ball moving through air

Answer: 

(d) Friction will act in case of ball moving through air always.

Question 7: What is the velocity gradient if frictional force is given to be 6N and eta(????) is given as 0.25 and the area of cross-section is 100m².

Solution:

Velocity gradient is 0.25

Question 8: Determine the force of friction in fluids if the coefficient of fluid friction is 0.25, velocity with which the fluid is flowing is 2m/s starting from the rest and the cross-sectional area is 50m².

Solution:

Question 9: Determine the coefficient of fluid friction if F is given 3N and the area of cross section is given 10m² also the velocity gradient given is 0.3/s.

Solution:

We know,

Coefficient of fluid friction is 1.

Fluid friction occurs between fluid layers that are moving relative to each other. This internal resistance to flow is called viscosity or viscous drag or fluid friction. In normal terms, the viscosity of a fluid is described as its “thickness” of the fluid. Thus, water is “thin”, having a lower viscosity, while honey is “thick”, having a higher viscosity. The less viscous the fluid, the greater its ease of deformation or movement.

All real fluids (except superfluids) offer some resistance to shearing and therefore are viscous. Although the term “fluid” includes both the liquid and gas phases, in common usage, “fluid” is often used synonymously with “liquid”. Liquids and gases are called fluids because they can be made to flow or move. In any fluid, the molecules themselves are in constant, random motion, colliding with each other and with the walls of any container. In this article, we will learn in detail about fluid friction, its properties, example and more.