00:01
For number 38, we're given this reaction.
00:04
And first, we're asked, what is the sum of the masses of the left side of the equation, and then the sum of the masses on the right side of the equation.
00:12
So in appendix b in the back, i looked up the masses of these.
00:18
So this was a mass of 1 .00785.
00:30
This lithium was a mass of 7 .016 -004.
00:38
This beryllium had a mass of 7 .01699 and the single neutron had a mass of 1 .008665 so part a a ask or the sums on the left side so that was just these two added together and i got 8 .0 023829 and then it asked what's the sum on the right side of the equation for part b so that was just adding these two and i got 8 .025594 and then part c said to subtract so we're taking just the right i mean the left minus the right side so left minus right we turn it to be negative 0 .001765.
02:06
And then we're asked to change that to energy.
02:09
So these are all measured in u's atomic mass units.
02:12
And now this one i'm converting to energy.
02:15
So i know there's 931 .5 in mega electron volts.
02:22
It's the same as one u.
02:25
So my u canceled.
02:27
And here my answer for part c in mega electron volts would be negative 1 .64 4 mega electron volts.
02:45
For part d, they give me expressions for velocities.
02:51
Initially, this lithium was at rest.
02:54
This hydrogen has a velocity of a lowercase v, and then after the collision, these both have a velocity of a capital v.
03:01
So i'm just putting the up there to remember.
03:03
And we're to write an expression in part d, we're to write an expression for conservation momentum.
03:13
Well, this was moving, this wasn't.
03:17
So total momentum before will be just the momentum of this, and we're called this the mass of a proton.
03:23
We're not supposed to put this number in now.
03:25
So the mass of the proton times the velocity of the proton, which is this lowercase v.
03:31
That's the total momentum before.
03:32
That would equal the total momentum after...