00:01
So let's say we have a yuccoa potential that has the form of negative r0 over r times u0 times e to the minus r over r0.
00:11
And r0 is 1 .5 times 10 to the negative 11 meters and u not, we're told, is 50 million electron volts.
00:25
And so the first part of this question asks us to find the expression for the force of the particles.
00:34
So our force, remember, as a function of r, is going to be the negative derivative of this with respect to r.
00:41
And so if we start to plug in our numbers, we'll have something like r0 times u.
00:46
And if we group a couple of terms together, we'll have 1 minus r squared, or sorry, negative 1 over r squared minus minus 1 over r times r not and this is times our negative exponential.
01:04
And then part b, we want to show that or to show the short range of the force.
01:10
We want to compute the ratio of the force at 3 or not.
01:16
So f of 3 to the force of r0 or at r0.
01:24
And do the same thing for 4 and 7.
01:29
So really, what we'll do is just let's replace this by some generic letter a.
01:34
And then we'll plug in a to be 3, 7, or sorry, 3, 4, and 7.
01:38
So if we compute this, we're going to have r0 over u0 times negative 1 over...