A helium nucleus (charge +2e) speeds by moving across a potential difference of -5kV. It starts from rest. How fast is it moving after it crosses the potential difference? Remember a helium nucleus has a mass of 34 atomic units (u) and 1u=1.66*10^-27kg.
Using energy conservation on helium nucleus
dKE = dPE
dKE = KEf - KEi
KEi = 0 J, since initial speed is zero
dKE = KEf = 0.5*m*Vf^2
dPE = Change in potential energy = q*dV
q = charge on helium = 2e
dV = -5 kV
So,
KEf = 0.5*m*Vf^2 = 2*e*dV
SEE THAT MASS OF HELIUM NUCLEUS SHOULD BE 4 ATOMIC UNITS, PLEASE CHECK YOUR VALUE AGAIN AND LET ME KNOW IF YOU STILL WANT ME SOLVE IT WITH 4 ATOMIC UNITS.
Vf = sqrt (4*e*dV/m)
Vf = sqrt (4*1.6*10^-19*5*10^3/(4*1.66*10^-27))
Vf = 6.94*10^5 m/sec
Please Upvote.
Again I will solve it with your given mass of 34 atomic unit if this one doesn't work. Let me know in the comments, but mass of helium should be 4 atomic unit. So please before downvote let me know in the comment section.
Get Answers For Free
Most questions answered within 1 hours.