# General Knowledge - Physics - Discussion

### Discussion :: Physics - Section 1 (Q.No.56)

56.

Mach number is used in connection with the speed of

 [A]. sound [B]. aircraft [C]. spacecraft [D]. ships

Explanation:

No answer description available for this question.

 Aparna said: (May 11, 2012) Mach refers to the speed of sound. A plane that travels at mach2 means it travels twice the speed of sound in air. The actual speed will vary a little depending on the altitude. Mach number is a measure of relative speed usually air and divided by speed of sound in that medium:. Is the mach number. Is the velocity of object relative to the medium used and. Is the velocity of sound in that medium. Mach number is the number of times the speed of sound of an object or a duct or the fluid medium itself move relative to each other. It is named after Austrian physicist Ernst Mach.

 Muhsin.N said: (Jun 20, 2013) Mach is the speed of sound. But answer is the aircraft. What is this?

 Oladapo Sodiq said: (Jul 2, 2014) In fluid mechanics, Mach number (M or Ma) is a dimensionless quantity representing the ratio of speed of an object moving through a fluid and the local speed of sound. M = v/vsound where, M is the Mach number, v is the velocity of the source relative to the medium, and vsound sound is the speed of sound in the medium. Mach number varies by the composition of the surrounding medium and also by local conditions, especially temperature and pressure. The Mach number can be used to determine if a flow can be treated as an incompressible flow. If M < 0.2-0.3 and the flow is (quasi) steady and isothermal, compressibility effects will be small and a simplified incompressible flow model can be used.

 Sujit said: (Dec 21, 2014) Mach number is a common 'ratio' unit of speed when one is talking about aircraft. By definition, Mach number is a ratio of the speed of a body (aircraft) to the speed of sound in the undisturbed medium through which the body is traveling. It is said that the aircraft is flying at Mach 1 if its speed is equal to the speed of sound in air (which is 332 m/s or 1195 km/hr or 717 miles/hour) An aircraft flying at Mach 2 is flying at twice the speed of sound in air, etc. SO ANSWER-B.

 Vicks said: (Aug 1, 2015) Aircraft is right answer because MACH NO is defined as the ratio of local speed of aircraft or any moving object to velocity of sound pertaining medium. Here velocity of sound use only for comparison factor nothing more than that. When we develop a aircraft so we generally express its speed in terms of MACH NO like 0.3, 0.7, 1.2. I think now its clear.

 Richa said: (May 13, 2016) Mach no in aircraft is not the speed, but the speed ratio. Mach no = object speed / speed of sound. It is used to indicate how fast one is moving when compared to the speed of sound.

 Deepak said: (Sep 24, 2016) The answer should be sound because any object traveling at a velocity equal or more than the speed of sound in that particular medium will have a Mach number, you can find mach number only when you have the speed of sound. So the mach number is only connected to the speed of sound.

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