18. When 1.6 mathrm(~kg) point charge is 15 mathrm(~m) from a second point charge, the gravitational force each one experiences is 573 mathrm(~N) . What is the mass of the second charge? Given: & Work: Formula: & Answer: 8.3 times 10^-12 mathrm(~kg) b. 1.2 times 10^11 mathrm(~kg) c. 1.2 times 10^12 mathrm(~kg) d. 8.5 times 10^12 mathrm(~kg) 19. Two electrons are 20 mathrm(~m) apart at closest approach. What is the magnitude of the maximum electric force that they exert on each other? (c=-1.60 times 10^-14 mathrm(C)) Given: & Work: Formula: & Answer: a. 1.2 times 10^-9 mathrm(~N) b. 5.8 times 10^11 mathrm(~N) c. 2.5 times 10^-6 mathrm(~N) d. 1.6 times 10^-11 mathrm(~N) 20. The force of attraction that a -40.0 mathrm(C) point charge exerts on a +108 mathrm(C) point charge has magnitude 4.00 mathrm(~N) . How far apart are these two charges? Given: & Work: Formula: & Answer: a. 1.38 times 10^3 mathrm(~m) b. 1.9 times 10^4 mathrm(~m) c. 3.12 times 10^4 mathrm(~m) d. 9.71 times 10^2 mathrm(~m)

Question

Answer 1

### Question 18:**Given:**- Mass of the first charge,

- Distance between charges,

- Gravitational force,

**Formula:**The gravitational force between two masses is given by Newton's law of gravitation:

Where:-

(gravitational constant),-

and

are the masses,-

is the distance.Rearranging for

:

**Substitute values:**

**Answer:**

---### Question 19:**Given:**- Distance between electrons,

,- Charge of an electron,

.**Formula:**The electric force between two charges is given by Coulomb's law:

Where:-

(Coulomb constant),-

and

are the charges,-

is the distance.Since both charges are electrons (

):

**Substitute values:**

**Answer:** The magnitude of the maximum electric force is approximately

.---### Question 20:**Given:**- Charges:

,- Force:

.**Formula:**Using Coulomb's law:

Rearranging for

:

**Substitute values:**

**Answer:**

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