# Viscosity and temperature, density is changing...

#### MPZ

What are the data you have plotted? I suggested plotting two curves - terminal velocity calculated using real density values, and terminal velocity calculated assuming constant density - and comparing them. You haven't done that.
why plot terminal velocity? cant i just plot the coefficients of dynamic viscosity since i am studying the relation between temp. and viscosity!

#### mjc123

Science Advisor
Because you have data for density and viscosity for this example. So you can do the reverse procedure - calculate the terminal velocity from the viscosity and the density, two ways, and compare them. Alternatively, you could calculate the TV from the viscosity and density data, then recalculate the viscosity from the TV values using a constant density, and compare the two sets of viscosity values. Either way, you should plot a graph of both sets of answers for comparison, which is what you didn't do.

#### MPZ

Because you have data for density and viscosity for this example. So you can do the reverse procedure - calculate the terminal velocity from the viscosity and the density, two ways, and compare them. Alternatively, you could calculate the TV from the viscosity and density data, then recalculate the viscosity from the TV values using a constant density, and compare the two sets of viscosity values. Either way, you should plot a graph of both sets of answers for comparison, which is what you didn't do.
ok. I will do this tomorrow

#### MPZ

Because you have data for density and viscosity for this example. So you can do the reverse procedure - calculate the terminal velocity from the viscosity and the density, two ways, and compare them. Alternatively, you could calculate the TV from the viscosity and density data, then recalculate the viscosity from the TV values using a constant density, and compare the two sets of viscosity values. Either way, you should plot a graph of both sets of answers for comparison, which is what you didn't do.
There is obviously going to be no difference. a change in a third decimal place will not affect the data right?

#### mjc123

Science Advisor
You want to think about significant figures rather than decimal places; a number with a value of, say, 0.0002 will definitely be affected by a change in a third decimal place! But I don't think that's the case with your data.

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