An alpha particle (helium nucleus with atomic number 2) has aninitial kinetic en

Question

An alpha particle (helium nucleus with atomic number 2) has aninitial kinetic energy of 7.31E-12 J. It then enters a region ofspace where the electric potential changes by an amount DV = 1.80E+7 V. What is its final kineticenergy?
I am using the Work-Energy Thereom: W = K = -eV.I'm not sure what I am doing wrong. I'm not understanding what thisalpha particle is, or just doing it wrong completely. An alpha particle (helium nucleus with atomic number 2) has aninitial kinetic energy of 7.31E-12 J. It then enters a region ofspace where the electric potential changes by an amount DV = 1.80E+7 V. What is its final kineticenergy?
I am using the Work-Energy Thereom: W = K = -eV.I'm not sure what I am doing wrong. I'm not understanding what thisalpha particle is, or just doing it wrong completely.

Explanation / Answer

   Since the change in potential is positive, particle is moving towards the positve plate and hence itsk.e. must decrease by same    amount as the work done by electricfield.    W   =   q *V   =   2 * 1.6 *10-19 * 1.80 *107   =   5.76 *10-12   J    Finalk.e.   =   initialk.e.   -   W    k.e.final   =   7.31* 10-12   -   5.76 *10-12   =   1.55 *10-12   J

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