Recent content by THA

It's regular 7-digit phone number, none of the 7 digit's can repeat. If that's not what you meant, then please clarify. That's what I was thinking, but I'm not really sure how to count the number's that start with 0 or 1. Would it be something like: P(10,7) - 2*P(10,6) ?

Problem details: I think if I pretend that N is also a number from 0-9, then there would be P(10, 7) numbers without repeats, but then that's too much and I'm not sure how I can subtract the number's that N is not supposed to have. The other way I was thinking is the last 6 numbers can be...

Let me see if I get this right, the potential to place the first proton is 0 so the work or potential energy required is 0. The potential to place the second proton, due to the first proton, is (k*q)/r and the potential energy is (k*q^2)/r. The potential to place the alpha particle is...

The question and detail: I setup the problem using energy conservation: K_a + U_a = K_b + U_b: K_a = total kinetic energy of the 3 charges when they're at rest U_a = total potential energy of the 3 charges when they're at rest K_b = total kinetic energy of the 3 charges when they're far...