(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Calculate the terminal velocity for a pollen grain falling through the air using the drag force equation. Assume the pollen grain has a diameter of 7 µm and a density of 0.3 g/cm3.

2. Relevant equations

Vterm= sq.rt of 2mg/pA

Volume= 4/3pi*r^2

Density = m/v

3. The attempt at a solution

I am given the answer but need to show how to get there.

Here is what I have, can someone point out where exactly I am going wrong?

Thank you!!

Vterm= sq.rt of 2mg/pA

p= air density of 1.3kg and

A = cross section of the pollen grain

A= 7µm = 0.000007m

To find mass of pollen grain:

radius= 1/2diameter

= 1/2(0.000007)

= 0.0000035m

Volume= 4/3pi*r^2

= 4/3pi(0.0000035)^2

= 5.13x10^-11 m^3

Density = m/v

m=DV

=0.3g/m^2 (5.13x10^-11 m^3)

= 1.54 x10^-11g

to kg = 1.54 x10^-14 kg

So, Vterm= sq.rt of 2mg/pA

Vterm = sq.rt. of 2(1.54 x10^-14 kg)(9.8m/s^2) / (1.3kg/m^2)(0.000007m)

=0.0018m/s

But I know this is wrong since I am given the final answer, which is 0.145m/s

I've worked it out so many times and I'm stuck. Please help.

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

**Physics Forums - The Fusion of Science and Community**

# Calculate the terminal velocity for a pollen grain

Have something to add?

- Similar discussions for: Calculate the terminal velocity for a pollen grain

Loading...

**Physics Forums - The Fusion of Science and Community**