Question: enter image description here

what i thought; see below.

enter image description here

we do not know density if i where to use that formula on the image file .

and i a m wondering why i was given the Reynolds number .

need help.

  • $\begingroup$ R in the question is not the Reynolds number, it is the universal gas constant. Use that to find the density. It can't be the Reynolds number, because it's units are given. Reynolds number is a dimensionless quantity! $\endgroup$
    – alephzero
    Oct 21, 2017 at 22:16
  • $\begingroup$ oh i see, so when given R what equation do we use to find density? $\endgroup$
    – Surdz
    Oct 21, 2017 at 22:27
  • $\begingroup$ Density = P / (R T) : easy mnemonic is prat .... That value of R is for air.... $\endgroup$
    – Solar Mike
    Oct 22, 2017 at 3:31

1 Answer 1


So the formula you need is Density = P /(R*T) and the value of R you have been given is for air.

Once you have re-worked your answer then you should calculate the Reynolds number and then you can check your result here : Drag on a sphere by NASA


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