October 30, 201411 yr Here is the scenario. You are sitting in the middle of a flat desert. A jet plan takes off several hundred miles from your location. The plane accelerates and reaches Mach 2. Though not technically correct, Mach 1 is many times seen/thought of as the speed of sound, so if something is going Mach 2, it's generally thought of as going "twice" the spend of sound. So, for purposes of this question, lets just say this plane is going twice the speed of sound, or 1,522.4 (761.2 x 2) miles per hour. So, exactly 1 hour after the plane reaches Mach 2, and it maintains that speed with a constant velocity, the plane passes directly over your head just a few hundred feet off the ground. My question is...how long will it take you to hear the plane AFTER it passes over your head, or will you hear it immediately?
October 30, 201411 yr Author Why am I in the middle of the desert? So you could answer this question. Duh.
October 30, 201411 yr It still will take a little while for you to hear it. I don't know why that is because I'm not a physics major, but I did sleep in a Holiday Inn Express last night.
October 30, 201411 yr Here is the scenario. You are sitting in the middle of a flat desert. A jet plan takes off several hundred miles from your location. The plane accelerates and reaches Mach 2. Though not technically correct, Mach 1 is many times seen/thought of as the speed of sound, so if something is going Mach 2, it's generally thought of as going "twice" the spend of sound. So, for purposes of this question, lets just say this plane is going twice the speed of sound, or 1,522.4 (761.2 x 2) miles per hour. So, exactly 1 hour after the plane reaches Mach 2, and it maintains that speed with a constant velocity, the plane passes directly over your head just a few hundred feet off the ground. My question is...how long will it take you to hear the plane AFTER it passes over your head, or will you hear it immediately? You would hear the plane immediately, I assume you are asking about hearing the original sonic boom?
October 30, 201411 yr You would hear it almost immediately because it passed only a few hundred feet from you.
October 30, 201411 yr The reason I said it still takes awhile is when I was in the airforce I was fortunate to see the SR71 several times in Okinawaa and I could be on the other side of the base when one would fly over and you wouldn't hear it until it was long past you, was kind of freaky. I have been wrong before so I can't say for sure and also because I was never standing directly under one by that short of distance as it flew over at mach 2 If I had, the real question would be, could you hear me soiling myself before you heard the SR71?
October 30, 201411 yr Author It still will take a little while for you to hear it. I don't know why that is because I'm not a physics major, but I did sleep in a Holiday Inn Express last night. But...will it take an hour for you to hear it, since the sound is only going half the speed the plane is?
October 30, 201411 yr But...will it take an hour for you to hear it, since the sound is only going half the speed the plane is? No, it doesn't take long, just a matter of seconds. For instance in Japan we would see the plane just about fly out of sight and then we'd hear the sound. I would guess you'd hear it that close within 5-10 secs...definitely not scientific and again I was never that close as you asked.
October 30, 201411 yr The reason I said it still takes awhile is when I was in the airforce I was fortunate to see the SR71 several times in Okinawaa and I could be on the other side of the base when one would fly over and you wouldn't hear it until it was long past you, was kind of freaky. I have been wrong before so I can't say for sure and also because I was never standing directly under one by that short of distance as it flew over at mach 2 If I had, the real question would be, could you hear me soiling myself before you heard the SR71?
October 30, 201411 yr Here is the scenario. You are sitting in the middle of a flat desert. A jet plan takes off several hundred miles from your location. The plane accelerates and reaches Mach 2. Though not technically correct, Mach 1 is many times seen/thought of as the speed of sound, so if something is going Mach 2, it's generally thought of as going "twice" the spend of sound. So, for purposes of this question, lets just say this plane is going twice the speed of sound, or 1,522.4 (761.2 x 2) miles per hour. So, exactly 1 hour after the plane reaches Mach 2, and it maintains that speed with a constant velocity, the plane passes directly over your head just a few hundred feet off the ground. My question is...how long will it take you to hear the plane AFTER it passes over your head, or will you hear it immediately? You need to know how long it took for the plane to accelerate from Mach 1 up to Mach 2 in order to properly answer. Reason being, as soon as the plane surpasses the speed of sound (call it 761.21 mph), it begins to separate itself from the sound wave it has created, and it continues to increase that separation at an increasing rate until it levels off its speed after reaching Mach 2. Think of it this way: Scenario 1 You are driving next to another car, and you are both traveling at 60mph. The other car maintains its 60mph speed while you speed up to 75mph and travel at that speed for 9 minutes 45 seconds before eventually increasing your speed up to 80mph. It takes you 15 seconds to increase speed from 75mph to 80 mph. So in the course of 10 minutes you have increased your speed by 20mph. However, you were traveling at 75 mph for the majority of those 10 minutes, all while the other car maintained a constant 60mph and you pulled away from it. Scenario 2 You are driving next to another car, and you are both traveling at 60mph. The other car maintains its 60mph speed while you speed up to 65mph and travel at that speed for 9 minutes 45 seconds before eventually punching it up to 80mph. It takes you 15 seconds to increase speed to 80 mph. So in the course of 10 minutes you have increased your speed by 20mph, but you were only going 65 mph for the majority of those 10 minutes. Again, the other car maintained its constand 60mph speed as you pulled away from it further. You can see how the distance between the two cars at the end of the 10 minute periods in the scenarios would be larger in Scenario 1 than it would be in Scenario 2, can't you? That's why in your original question regarding the plane and the speed of sound you would need to know how long it took to move from Mach 1 to Mach 2.
October 30, 201411 yr While Big V is avoiding some responses in this thread I have a couple of other questions for anyone in the know. 1. How fast do sonic boom sound waves move? The speed of sound or something else? I know it sounds like a stupid question but that is okay. 2. The original sonic boom would have taken place around 1500 miles away, how much does sound dissipate over distance keeping in mind a dessert is somewhat consistent terrain?
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