x Masteringphysics: Assign x MasteringPhysics: Chapter 21-Google Chrome https://

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x Masteringphysics: Assign x MasteringPhysics: Chapter 21-Google Chrome https://session masteringphysics.com/myct/itemview?assignmentProblemID 73549831 PHY 242 University Physics ll Spring 2017 signed in as Nicholas Danish Bep Chapter 21 Problem 21.73 Resources e previous 11 of 11 I return to assignmer Problem 21.73 Part A A water droplet of radius 1.7x10 2 mm remains If the downward-directed electric field of the Earth is 190 N/C how many excess electron charges must the stationary in the air water droplet have? Express your answer using two significant figures. My Answers Give Up Submit Incorrect; Try Again: 3 attempts remaining Continue

Explanation / Answer

Info Given:

Radius of the droplet: .000017 m

E = 190 N/C

Since there is no equation that can relate these two, we'll have to first use the radius to find mass of the droplet.

m = d(4/3)pr3

d = (density) given = 1000

m = (1000)(4/3)(pi)(.000017)^3

m = 2.05e-11

Now that we have enough variables, we can use an equation to relate E with m and g. Eq is the electric force, mg is the force of gravity.

Eq = mg

(190)(q) = (2.05e-11)(-9.8)

q = 1.06e-12

To find the number of electrons, we just divide by the electron charge, 1.0602e-19.

Number of extra electrons = 1.06e-12/1.0602e-19 = 9.9e6 = 1.0e7

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