A proton is put on the positive Y axis a large distance (100km) from the origin. What is the minimum speed required in the - Y direction so the proton will just reach the point (0,20) cm?

Answer 1

Is there some sort of repelling positive charge at the origin or what ?
If so the kinetic energy at infinity has to equal the potential energy at 20 cm

Answer 2

0,0 is the origin there is no repelling charge

Answer 3

Then there is no force on the proton and it will keep going forever with infintesimal velocity.

Answer 4

So what's the minimum speed ?