Q1. The ancient Greeks thought that atoms were tiny spheres that could not be divided into anything smaller. Since then, different discoveries have led to the model of the atom changing.
Some of the discoveries are given in the table below.
The mass of an atom is concentrated in the nucleus.
A
Electrons orbit the nucleus at specific distances.
B
The nucleus contains neutrons.
C
The nucleus contains positively charged protons.
D
(a)
Which discovery was the earliest?

Iwannasay c is the most accurate

Pe = 1/2k(x)^2  and .05n/m = .05x10^-9m = x 

Answer: a charge of -1.0  × 10⁻⁴ c must be placed  at x = 26 m.the sign of the charge will be the same sign as the  -4.0  µc charge.======electricstatic force between two point charges  is given by    where k is coulomb's constant,  8.99×10⁹  n·m²/c², q₁ and q₂ are the point charges, and r is the distance between the two point charges.assign positive to q₁let q₁ =  6.0 µc, q₂ = -4.0  µc, q₀ represent the charge at the origin, and q₃ represent this new charge to place.the charge at the origin q₀ would experience the following force f₀₁ from q₁, with r = 6.0 m (note that 1  µc = 10⁻⁶ c)    the force from q₂    the force from q₃    the net force on the origin charge, q₀, has to be zero for no electrostatic forcehaving an equation where k and q₀ can be divided out of the equation will allow us to solve for q₃    isolating:     a charge of -1.0  × 10⁻⁴ c must be placed  at x = 26 m.the sign of the charge will be the same as the  -4.0  µc charge