If you wonder how such large objects as cars, planes and ships move around, and why they need so much power, we are going to get into more detail on why they require a lot of power to move, what is air resistance and why the shape of the object is important when we need to consume less power and move easier.
What is aerodynamic drag
A moving object has speed and there is the force that opposes its movement – resistance. When we move an object through a fluid this type of resistance is called aerodynamic drag. It is a force that is pulling the object to the opposite side of its movement. It is generated because of the difference in velocity between the fluid and the object.
Depending on the object’s surface and shape the drag can be different. For example, if the object has a smooth surface, its drag would be less, due to less friction created between the fluid and its surface. If the object has a rough surface and the viscosity of the fluid is high, then there would be a lot more drag forces, which will decrease its speed.
The shape of the object is also important. Deeding on the difference between the velocity of the object and the fluid, the local velocity and pressure of the fluid will be different on different surfaces due to its shape.
Why is air resistance important
Air resistance is often used when we design the shapes of cars, boats, planes, and many more. This is really important when we want to increase its speed and decrease its power consumption.
The more air resistance it has, the less efficient it is. So for example, if we have a specific shape of a car, that moves at 100mph and we have the same power but in better form that has a lot less drag, it will require less energy to move with the same speed, since there are fewer forces acting against its movement.
What is drag coefficient
This is a quantity that is used to quantify the resistance of an object in the fluid. The coefficient is used in the equation, and a lower drag coefficient means that the object has less aerodynamic drag. It comprises two basic contributors to the drag of the object – skin friction and form drag.
Examples of drag coefficient of common objects
A cube has a coefficient of around 1.
Half-sphere – 0.42.
Cone – 0.50.
A sphere – 0.47.
Streamlined body – 0.04.
The shape of the object is really important when designing automobiles for example. As you have probably seen, many of the fastest cars in the world have a very specific shape, they are not too tall or wide, their fronts are usually shaped so that the air can slide over them.
The air resistance in cars is mostly used to reduce power consumption and if the car is designed to be driven at high speed, its shape is designed in a way to create pressure above the car so that the force, presses the car downwards toward the road. This gives the car a better grip on the road, around corners, and a better position for higher speeds.