Two particles each have a mass of 5.5 10-3 kg. One has a charge of +4.8 10-6 C, and the other has a charge of -4.8 10-6 C. They are initially held at rest at a distance of 0.88 m apart. Both are then released and accelerate toward each other. How fast is each particle moving when the separation between them is one-third its initial value?

Question

Two particles each have a mass of 5.5  10-3 kg. One has a charge of +4.8  10-6 C, and the other has a charge of -4.8  10-6 C. They are initially held at rest at a distance of 0.88 m apart. Both are then released and accelerate toward each other. How fast is each particle moving when the separation between them is one-third its initial value?

Elena · Answer

k =9•10⁹ N•m²/C²,
q=4.8•10⁻⁶ C
m=5.5•10⁻³ kg
r=0.88 m

PE₁-PE₂=2KE
-kq²/r +3kq²/r =2mv²/2
2kq²/r =2mv²/2
kq²/r =mv²/2
v=sqrt( kq²/rm) =
=sqrt{9•10⁹•(4.8•10⁻⁶)²/0.88•5.5•10⁻³} =
=6.55 m/s