Question

If Mo is the mass of oxygen
isotope ,Mp and Mn are the masses of a proton and a neutron respectively the nuclear binding energy of isotope is

Answer 1

@Vincent-Lyon.Fr pls.help

Answer 2

@astrophysics pls...help...
@rvc @priyar

Answer 3

hey hi
please refer to this link : http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/nucbin.html

Answer 4

@rvc i know this....bt what i want to say is that i m having a -ve sign in the ans

Answer 5

I know dat nuclear binding energy is calculated by difference in mass of reactants n products...

Answer 6

Multiplied vid c^2

Answer 7

Like my ans is (8Mp+9Mn -Mo)c^2

Answer 8

N their ans is -ve of it..

Answer 9

hmm..wait
@ganeshie8 help

Answer 10

Did u get my doubt ??

Answer 11

m confused

Answer 12

Confused in -ve sign or d whole ans...

Answer 13

@rvc plss..reply...

Answer 14

@IrishBoy123 help me

Answer 15

So what's bothering you is not the magnitude, but the negative sign?

Answer 16

Yep ...@parthkohli...this is nuclear energy n here signs are meant to be of gr8 meaning

Answer 17

OK, binding energy whenever attractive forces are involved is treated to be of a negative sign.

We assume that zero potential energy is when all masses are held at infinite separation.

A way to understand this is you'll have to do positive work against the attractive force to bring them to infinite separation.\[\rm E_{binding}+\text{some positive work} = E_{infinity}= 0\]\[\Rightarrow \rm E_{binding} = - (\text{some positive work)} = \text{some negative number}\]So that is why binding energy in case of attractive forces is negative.

Answer 18

@parthkohli it has been clearly mentioned in binding energy that it is equal to
(mass of reactants-mass of products)*c^2

Answer 19

Err modern physics. -_-

Answer 20

Yep @ParthKohli is correct

Answer 21

`-ve` sign means ATTRACTIVE FORCE.

Answer 22

Ok @samigupta8 i got your doubt

Answer 23

First tell me what is binding energy ?

Answer 24

Mass of protons and neutrons forming nucleus is always less than mass of nucleus ...this thing dat is d difference between them appears as mass defect which when multiplied vid c^2 gives us binding energy

Answer 25

@parthkohli yeah...it'zz dat nuclear physics .....

Answer 26

Sorry greater than....

Answer 27

what mayank said is that the negative sign is because it is an attractive force

Answer 28

But if u go through any of the books u will find whatever b d case v always take binding energy as this only...the definition posted above...by me

Answer 29

It's always an attractive force bt i never came up vid d sign reversal jst like in dis problem...
So here is d major doubt of dis problem...
I m greatly concerned by dis sign...nothing else...

Answer 30

maybe it means the resulting isotope is unstable?

Answer 31

Bt it's never this way @baru
How can u arrive at it so easily ?

Answer 32

yes we usually take binding energy to be positive.

Answer 33

@priyar whom r u supporting here?

Answer 34

u

Answer 35

i have no idea... i'm just guessing

Answer 36

@baru it's like that i hve never came across any such thing before so i can't swallow it so easily dat it can be -ve of what i m getting...

Answer 37

Don't you all think that there needs to be d ans which i m telling u all...i seriously donno whether my doubt is rubbish or not
Bt guys...i m literally for sure confused in it...

Answer 38

binding energy is the energy that holds the protons and neutrons together.. to break the nucleus to its constituents we need to supply energy equal to the binding energy..otherwise its the other way around.. in problems we usually find the magnitude which is same in both cases..

Answer 39

i dont really know... i'm just going by whatever info is on this thread
u said that the nucleus is lighter than the sum of its constiutents

so in the formula (mass of reactants-mass of products)*c^2
if reactants mean constituents and produduct means nucleus,
then the answer is always positive

Answer 40

Correct that's what is my argument here...why ans is -ve den

Answer 41

yes binding energy is more properly defined as: "Nuclear binding energy is the energy required to split a nucleus of an atom into its component parts: protons and neutrons, or, collectively, the nucleons. "
and, the binding energy of nuclei is always a positive number, since all nuclei require net energy to separate them into individual protons and neutrons.

Answer 42

So as i said before... we supply an energy equal to the binding energy to split the nucleus... and that is also the definition of nuclear binding energy so we take it to a POSITIVE quantity always which is also justified by Einstein's eq

Answer 43

So basically v all r ending up vid same conclusion ryt....in different manners ....lol ...

Answer 44

yes..our definition is like that..a bit confusing...but we always define it as "energy required" which stand for +ve..
(in my opinion).. i haven't come across a negative binding energy so far..

Answer 45

Thanks.....bt dis is sumthing i know already i wud like to know if their ans is correct or mine.....plss...if any of u cum across d reason of it. .pls do tell me ....bcz dis is sumthing dat pesters me to the core

Answer 46

@samigupta8 First read the definition !
You can notice that BINDING ENERGY IS AN ATTRACTIVE FORCE.It is natural.
So, why we always use `-ve`sign.

Take an example:-
Centripetal force is also acts at centre.So it is attractive in nature.
So,why can't we add `-ve`sign to it ?

Answer 47

yep @mayankdevnani i agree

Answer 48

thank you !

Answer 49

So @mayankdevnani you want to say that it should occur in every question ..
isn't it??

Answer 50

yep!

Answer 51

like centripetal force

Answer 52

Always an attractive force.
It is understood.

Answer 53

@mashy

Answer 54

There is nothing like confusion.

Answer 55

Try to understand with easiest example like centripetal force.
Try to co-relate with it.

Answer 56

@mayankdevnani haven't u done questions based on this ....where v need to calculate binding energy n it has to be sum of nucleons-sum of nucleus.....
Pls...@mayankdevani u try to understand my point of view.....sorry if u r feeling dat i m trning out to be rude

Answer 57

i have done many questions

Answer 58

Then each time u did the same thing told by you...or as told by me

Answer 59

first tell me
mass of nucleus is greater or mass of nucleons

Answer 60

Mass of nucleons

Answer 61

and what is the formula of BE

Answer 62

N so mass defect is mass of nucleons- mass of nucleus

Answer 63

Mass defect *c^2

Answer 64

why would you use
mass defect=mass of nucleons-mass of nucleus ?

Answer 65

why not this :-
mass defect=mass of nucleus-mass of nucleons

Answer 66

wait wait @Michele_Laino !!!! help

Answer 67

Yrr mayank ...ruko hangouts kholo apna i will send sumthing

Answer 68

okay !

Answer 69

@rvc michele sir is a good friend of mine.
Like we are BESTIEEES

Answer 70

lol ikr

Answer 71

you know ! wow

Answer 72

is the isotope
\[\huge _8^{17}{\text{O}}\]?

Answer 73

nope

Answer 74

Yep

Answer 75

Yehi toh h ...

Answer 76

probably \[\large \bf _8^{18}O\]

Answer 77

Mayank @michele sir is ryt ...

Answer 78

https://en.wikipedia.org/wiki/Isotopes_of_oxygen
yep there are 3

Answer 79

mine is correct too

Answer 80

Arey i m talking about d present question

Answer 81

first answer my question

Answer 82

in that case the requested binding energy is:
\[\Large BE = \left\{ {\left( {8{m_p} + 10{m_n}} \right) - {m_{isotope}}} \right\}{c^2}\]
since we have 8 protons and 18-8=10 neutrons

Answer 83

why would you use
mass defect=mass of nucleons-mass of nucleus ?

why not this :-
mass defect=mass of nucleus-mass of nucleons?

Answer 84

Vicg question

Answer 85

Exactly @michele_laino sir...

Answer 86

of course if the isotope is:
\[\huge _8^{17}{\text{O}}\]
then the answer of @samigupta8 is correct!

Answer 87

Thank you...@michele_laino n obviously d isotope mentioned in question is dis one only

Answer 88

lol
atlast !

Answer 89

@mayankdevnani please refer to my tutorial:
http://openstudy.com/study#/updates/569003b1e4b09cb8736d02b5

Answer 90

thank you so much sir!
m glad that you helped us

Answer 91

So @Michele_laino sir my ans is correct ryt...
Bt in d ans key it is giving -ve sign in front of d expression u came with finally

Answer 92

the minus sign depends on the definition we use

Answer 93

How?

Answer 94

some authors define the binding energy in this way:
\[\Large - BE = \left\{ {\left( {8{m_p} + 10{m_n}} \right) - {m_{isotope}}} \right\}{c^2}\]

Answer 95

Seriously ??
Like then whom to trust upon ??