00:01
We solved the given problem by first writing the generalized formulation reaction that is x is plus small x gives y, where x is a target nucleus and x is the incident light particle where y is the excited compound nucleus here in this case n e 20 we have here.
00:28
We assume x is initial.
00:30
At rest then by using a law of conservation of energy we can write m of x times c square plus m x c square plus k x kinetic energy is equal to m y c square plus k y c square plus k y plus e y where we have m x capital x and m small x and m capital y are the masses where kx and k y are the kinetic energies.
01:06
Ey here is the excitation energy of y.
01:11
Then by using a law of conservation of momentum we can write px is equal to p y.
01:18
Now we can write k y is equal to p y squared divided by two m y that is equal to p x squared divided by two m y that is this gives us mx divided by m y times kx.
01:40
So our k y is equal to m x divide by m y times kx.
01:46
Then we can write m x, mx times c squared plus, so this is capital x here, plus mx small x, c square, plus kx is equal to m y c square plus kx is equal to m y c square plus plus mx or my times kx plus ey.
02:15
From here we can solve for kx over kx will become my divided by my minus mx this times my minus m x minus m x m x x x times m x for part a of the problem, let small x represents the alpha particle and the capital x represents the oxygen 16 nucleus.
02:49
Then we can write mi minus mx minus m small x times c square.
02:57
We can write this by substituting values 19 .99244.
03:04
Atomic mass units minus 15 .99491 atomic mass units minus 4 .00260 units times the energy associated with one atomic mass unit which is 931 .5 mega electron volt per u.
03:30
So this gives us minus 4 .4 .5.
03:35
0 .722 mega electron volt.
03:39
Then we can find the kinetic energy of alpha particles.
03:44
So k alpha will be then 19 .99244 atomic mass unit divided by 19 .99244.
03:57
Atomic mass unit minus 4 .00260 atomic mass unit times minus 4 .00260 atomic mass unit times minus 4.
04:06
722 mega electron volt plus 25 mega electron volt this gives us approximately 25 .4 mega electron volt for part b of the problem, let's small x represents the proton and the capital x represents the f -19 fluorine nucleus then we can write mi m .y minus m capital x minus m small x times c square will be 19 .992 -44 minus 18 .99841.
04:52
This is in atomic mass unit, so i'm skipping the units here, minus 1 .00783.
05:00
This times 990841...