Question

A flower falls to the bottom of a lake. Once it is on the bottom, it will release pollen (a little sphere) which begins to float towards the surface The drag force on a sphere in fluid is F​drag​​=6πrηv, where r=100 μm is the radius of the pollen, η=10^−3 Ns/m^2 is the viscosity of water and v is the velocity of the pollen. The density of pollen is p​​=300kg/m​^3​​ and the density of water is ρ​w​​=1000kg/m​3​​. The pollen floats due to the buoyant force, which is a force towards the surface of the lake equal to the weight of water displaced by the pollen (this weight is ρ​w​​V​p​​g, with V​p​​ the volume of a pollen particle).

a)What is the pollen's terminal speed in m/s?

b)If the pollen starts at rest what percentage of its terminal velocity has it reached after 1 ms?

Answer 1

1. bottom one is first page