Question Concerning Electric Potential Equation Two protons are held 100 nm away

ID: 1883469 • Letter: Q

Question

Question Concerning Electric Potential Equation

Two protons are held 100 nm away from each other and then one is released. How fast is it moving when is 300 nm from the stationary proton?

A. 959 m/s

B. 1360 m/s

C. 7830 m/s

D. 2350 m/s

E. 1170 m/s

I understand the correct answer is B (1360 m/s), however, my question is concerning the equation from the electric potential equation.

Step 1: Balance the total energy Ui=Uf+Kf

Question 1) In general, How should I know to use U as opposed to V

V = (kq)/r

U = (kq1q2)/r

Question 2) Could I use the kinematic equations to find the same answer?

I would solve F=ma to become a =F/M where F = columns law

Would the be making the assumption F is constant? Which would be wrong in this case since F is proportional to 1/r?

Q 1. value of potential or its function is given, then we use U = qV

But when point charges are given, then we can use U and both formula given for U and V can be uses as U =q V so both formulas are actually same.

Q 2 . cannot use kinematics equations because force is not constant and increases as charges comes closer.

F is proportional to 1/r2 not 1/r according to couulombs law

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.