Asmall piece of dust of mass m = 4.1 µg travels through an electric air cleaner in which the electric field is 466 n/c. the electric force on the dust particle is equal to the weight of the particle.

(a) what is the charge on the dust particle?
c

(b) if this charge is provided by an excess of electrons, how many electrons does that correspond to?
electrons

Explanation:

mass, m = 4.1 x 10^-6 g

Electric field, E = 466 N/C

Electric force = weight

(a) Electric force = q x E = m x g

where, q be the charge on the dust particle.

q x 466 = 4.1 x 10^-6 x 9.8

q = 8.62 x 10^-8 C

(b) Number of electron  = charge / charge of one electron

n = 8.62 x 10^-8 / (1.6 x 10^-19)

n = 5.4 x 10^11

that tool is called an altimeter which measures your altitude which can be used to tell which atmosphere you are currently in, including the stratosphere.

hope this ! : )