🎇 Fireworks 🎇 and Sonic booms
Below is the link of a fireworks 🎇 for you to enjoy.
When recording the video, the audio level was reduced so it does not sound as loud as if you were present at the 🎇 show.
Why do fireworks sound so loud. Is the explosion so violent that it it sound loud?
If you say yes, you are not correct.
The bangs that you hear are sonic booms. A sonic boom occurs when something travels faster than the speed of sound.
Why do sonic booms occur?
I will use a boat moving through water to try to explain sonic booms.
In order for the boat to move, it has to push aside the water in front of it. Some of the water is pushed a little ahead of the boat and most of it will flow to the 2 sides of the boat. The picture we see is like a V shaped bow of waves with the sharp point of the bow at the front of the boat and the 2 sides of the V on the 2 sides of the boat.
The waves on the 2 sides of the boat will collapse and come back together after the boat has moved on. So the boat is surrounded by a V-shaped bow and a turbulent area just behind the boat.
The faster a boat travels, the greater will be the bow of waves and turbulence behind the boat.
The resistance of the water against the forward movement is proportional to the square of the speed of the boat. Doubling the speed means quadrupling the resistance.
The V-shaped bow of waves and turbulent area will follow the boat around. The greater the speed of the boat, the more violent will be the water and the water at the 2 sides will have enough energy to spray up into the end.
What will happen if the speed of the boat increases to and the exceed the speed of sound? Instead of being able to follow the boat as it moves forward, the waves and turbulence gets left behind by the boat which is travelling faster than the speed of sound.
By the time the boat is almost at the speed of sound, the water movement would have been incredibly violent. As the boat exceeds the speed of sound the coming back of the water left behind is so violent that it is a sonic boom.
When an object moves through air, it has to push air aside like the boat has to push water aside.
As the object exceeds the speed of sound there is sonic boom created by the air waves. The sonic boom is sound waves of air. Sound we hear are actually air waves. Eg as a guitar string vibrates, the vibration of the guitar string creates waves of air which is sound produced by the guitar.
As the fireworks fly up into the air, its fuse is burning. When the fuse reaches a big mass of highly combustible substance, the burning of the substance is so hot that it heats up the air around it and causes the air to expand greatly and move away from the super hot area. The movement of air is so fast that it is faster than the speed of sound and we hear a sonic boom.
So the bang that we hear caused by air movement faster than the speed of sound.
Here is the link for an experiment where I produced a sonic boom in a laboratory
The multi coloured lights we see is the sight of the combustible material burning. The presence of different substances in the combustible material produces the different colours.
Air resistance against a car is also proportional to the square of the speed of the car. The amount of resistance against a car moving at 120 kph is 1.5 x 1.5 = 2.25X of a car travelling at 80 kph. So travelling at 120 kph burns up a lot of fuel to overcome the air resistance.
By reducing your speed to 80 kph, you save a lot of money on fuel and contribute less Carbon dioxide from the burning of fuel. Both of these are important because of climate change and the current state of the economy.
In order for this post to not be excessively long, it will be continued in another post where we talk about thunder, lightning, mach numbers and aircrafts.
