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## Homework Statement

K i need help with like 3 phyics problem on electric forces / charges.

1. One gram of copper has 9.48 10^21 atoms, and each copper atom has 29 electrons.

(a) How many electrons are contained in 1.08 g of copper?

_________ electrons

b. What is the total charge of these electrons?

__________ C

2. Calculate the net charge on a substance consisting of a combination of 7.5 10^13 protons and 4.2 10^13 electrons.

___________ C

3. An alpha particle (charge = +2.0e) is sent at high speed toward a gold nucleus (charge = +79e). What is the electric force acting on the alpha particle when the alpha particle is 4.8 10^-14 m from the gold nucleus?

_______________ N

## Homework Equations

Elctron -1.6 x 10^-19

Proton: 1.6 x 10^-19

Coulombs Law: Felectric = Kc (q1*q2)/r^2

## The Attempt at a Solution

alright iv been having trouble since our teacher did not teach us anything about these barley and the book doesnt help at all.

1st one i dont know where to start.

2nd one i tried just simply adding them together and that didnt work and then i tried using pythagorm theorm because iwas maybe thinking that the net force you need to find like the triange.

3rd one i plugged into the columbs law and i got 6.2x10^38 and i think i got that wrong too?

Any help please?