The nucleus of a 125Xe atom (an isotope of the element xenon with mass 125 u) is 6.0 fm in diameter. It has 54 protons and charge q=+54e (1 fm = 1 femtometer = 1×10−15m.) Hint: Treat the spherical nucleus as a point charge. Part A Part complete What is the electric force on a proton 1.0 fm from the surface of the nucleus? Express your answer in newtons. Fnucleusonproton F n u c l e u s o n p r o t o n = 780 N SubmitPrevious Answers Answer Requested Part B What is the proton's acceleration? Express your answer in meters per second squared.

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Answer:

A: [tex]777.6\ N.[/tex]

B: [tex]\rm 4.656\times 10^{29}\ m/s^2.[/tex]

Explanation:

Given:

  • Charge on the 125 Xe nucleus, [tex]\rm q = +54e.[/tex]
  • Diameter of the 125 Xe nucleus, [tex]\rm d=6.0\ fm = 6.0\times 10^{-15}\ m.[/tex]
  • Distance of the proton from the surface of the nucleus, [tex]\rm a=1.0\ fm = 1.0\times 10^{-15}\ m.[/tex]

Part A:

Coulomb's law states that the electric field due to a charged sphere of charge Q at a point r distance away from its center is given by

[tex]\rm E=\dfrac{kQ}{r^2}.[/tex]

where, k = Coulomb's constant whose value = [tex]9\times 10^9\ \rm Nm^2/C^2.[/tex]

Therefore, the electric field due to the nucleus at the proton is given by

[tex]\rm E=\dfrac{kq}{r^2}=\dfrac{(9\times 10^9)\times (+54 e)}{r^2}[/tex]

  • [tex]\rm e[/tex] = elementary charge, having value = \rm 1.6\times 10^{-19}\ C.
  • [tex]\rm r[/tex] = distance of the proton from the center of the nucleus =[tex]\rm a+\text{Radius of the nucleus}= a + \dfrac d2 = 1.0+\dfrac{6.0}2=4.0\ fm = 4.0\times 10^{-15}\ m.[/tex]

Therefore,

[tex]\rm E=\dfrac{(9\times 10^9)\times (+54 \times 1.6\times 10^{-19})}{(4.0\times 10^{-15})^2}=4.86\times 10^{21}\ N/C.[/tex]

The electric force on a charge q due to an electric field is given as  

[tex]\rm F=qE[/tex]

For the proton, [tex]\rm q = e =1.6\times 10^{-19}\ C.[/tex]

Thus, the electric force on the proton is given by

[tex]\rm F = 1.6\times 10^{-19}\times 4.86\times 10^{21}=777.6\ N.[/tex]

Part B:

According to Newton's second law,

[tex]\rm F=ma[/tex]

where, a is the acceleration.

The mass of the proton is [tex]\rm m_p=1.67\times 10^{-27}\ kg.[/tex]

Therefore, the proton's acceleration is given by

[tex]\rm a = \dfrac{F}{m_p}=\dfrac{777.6}{1.67\times 10^{-27}}=4.656\times 10^{29}\ m/s^2.[/tex]

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