Question

Which of the following is a supersonic speed?



Mach 0.005

Mach 0.05

Mach 0.5

Mach 5

Answer 1

Do you know why we use the word "Mach"?

Answer 2

no

Answer 3

Well, because we're talking about a "Mach number."

So, if we look at the first one, 0.005, we don't want to say it is 0.005 of something. We want to say it is a Mach number.

And a Mach number is actually a ratio. It is
\(\rm\dfrac{speed\ of\ an\ object\ in\ a\ fluid}{speed\ of\ sound\ in\ that\ fluid}\)

So, you can say
\(\large\dfrac{v_\text{object}}{v_\text{sound}}\)

So, is that much okay with you?

Answer 4

oh, so it would b the last choice?

Answer 5

Yep! :)

Answer 6

Thank you :D :D

Answer 7

That's the only option where the object speed is greater than the speed of sound,

which is to say that the object has a supersonic speed.

You're welcome! :)