Question

You are a member of a group designing an air filtration system for allergy suffers. To optimize its operation, you need to measure the mass of the common pollen in the air where the filter will be used To measure the pollen's mass, you have designed a small rectangular box with a hole in one side to allow the pollen to enter. Once inside the pollen is given a positive electric charge and accelerated by an electrostatic force to a speed of 1.4 m/s. The pollen then hits the end of a very small, uniform bar which is hanging straight down from a pivot at its top. Since the bar has a negative charge at its tip, the pollen sticks to it as the bar swings up. Measuring the angle that the bar swings up would give the particle's mass. After the angle is measured, the charge of the bar is reversed, releasing that particle. It's a cool design but your friend insists it will never work. To prove it she asks you to calculate the length of the bar which would give you a reasonable angle of about 10° for a typical pollen particle of 4x10-9 grams. Your plan calls for a bar of 7x104 grams. Is she right?