In class we dropped a chickpea to measure the terminal speed vT and thus the viscosity of olive oil and other liquids. The drag force on a chickpea falling through olive oil is given by Fdrag = 6πηRvT. It points in the upward direction, while the weight mg points downwards.
(i) If the chickpea falls 12 cm in 2 seconds, what is the terminal speed vT?
(ii) If the viscosity is 85 mPa.s and the radius is 3 mm, what is the drag force?
(iii) Based on this viscosity, what is the density difference between the chickpea and the olive oil?
(iv) How would the time needed for the chickpea to fall 12 cm change if it was traveling through honey instead? Assume that the viscosity of the honey is 100 times that of the oil and the density difference between chickpea and honey is 1.2 g/cm3 . Does it make sense to use the chickpea to measure the viscosity in this case?