Problem 20.60 Two 3.0-cm-diameter disks face each other, 1.0 mm apart. They are

Question

Problem 20.60

Two 3.0-cm-diameter disks face each other, 1.0 mm apart. They are charged to ± 10 nC .

Part A

What is the electric field strength between the disks?

Express your answer using two significant figures.

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Part B

A proton is shot from the negative disk toward the positive disk. What launch speed must the proton have to just barely reach the positive disk?

Problem 20.60

Two 3.0-cm-diameter disks face each other, 1.0 mm apart. They are charged to ± 10 nC .

Part A

What is the electric field strength between the disks?

Express your answer using two significant figures.

SubmitMy AnswersGive Up

Incorrect; Try Again; 9 attempts remaining

Part B

A proton is shot from the negative disk toward the positive disk. What launch speed must the proton have to just barely reach the positive disk?

Explanation / Answer

1. E = Q/(e0*A)

A = pi*r^2, where r = 1.5 cm

E = 10*10^-9/(8*85*10^-12*3.14*0.015^2)

E = 20815.12 N/C

2. F = qE = 1.6*10^-19*20815.12 = 3.33*10^-15 N

F = ma

a = 3.33*10^-15/(1.67*10^-27) = 1.99*10^+12

V^2 = u^2 + 2*a*s

V = sqrt(0^2 + 2*1.99*10^12*10^-3) = 63087.24 m/sec

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