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# M1 momentum question Watch

1. How should i approach question 5bi? i tried it and keep getting loops...
2. (Original post by alesha98)

How should i approach question 5bi? i tried it and keep getting loops...
Please post what you have tried.
3. (Original post by notnek)
Please post what you have tried.
i know it is wrong and somehow maybe i misread the question. so i did:
By solving vertically:T1+T2 = 25g + Mg
From A25g)(2.5) + 5Mg = 4.5T2
From C:0.5Mg+4.5T1 = 50g
and then i solved it simutanuosly
4. (Original post by alesha98)
i know it is wrong and somehow maybe i misread the question. so i did:
By solving vertically:T1+T2 = 25g + Mg
From A25g)(2.5) + 5Mg = 4.5T2
From C:0.5Mg+4.5T1 = 50g
and then i solved it simutanuosly
Well you can't solve those simultaneously as the three equations are linearly dependent. You can use them in a fashion, but there is a much simpler method:

If the weight at B is a maximum, what can you deduce about the tension at A? Can you see another way to do it now?
5. (Original post by ghostwalker)
Well you can't solve those simultaneously as the three equations are linearly dependent. You can use them in a fashion, but there is a much simpler method:

If the weight at B is a maximum, what can you deduce about the tension at A? Can you see another way to do it now?
i dont know what it is telling me when the weight at B is maximum, can you explain to me please?
6. (Original post by ghostwalker)
Well you can't solve those simultaneously as the three equations are linearly dependent. You can use them in a fashion, but there is a much simpler method:

If the weight at B is a maximum, what can you deduce about the tension at A? Can you see another way to do it now?
and what do you mean by linearly dependent?
7. (Original post by alesha98)
and what do you mean by linearly dependent?
They are essentially the same thing. You don't have enough independent equations to give you the solutions you require.

The equations of a linear system are independent if none of the equations can be derived algebraically from the others. If a system is not independent, it is dependent.
8. (Original post by alesha98)
i dont know what it is telling me when the weight at B is maximum, can you explain to me please?
Suppose you pile more and more weight onto B, and the strings don't break, what's going to happen?
9. (Original post by Kvothe the arcane)
They are essentially the same thing. You don't have enough independent equations to give you the solutions you require.

The equations of a linear system are independent if none of the equations can be derived algebraically from the others. If a system is not independent, it is dependent.
thankyou and yes, thats why i keep getting loops. I dont know what it is telling me when the weight of B is maximum
10. (Original post by alesha98)
and what do you mean by linearly dependent?
In this case you have three unknowns and effectively only two equations, since the third can be derived from the other two (hence dependent). And that's not enough to solve the system of equations.
11. (Original post by ghostwalker)
Suppose you pile more and more weight onto B, and the strings don't break, what's going to happen?
A goes up, B goes down. i think i get it, so when the weight on B is maximum, the tension in A is 0 because although the beam remain in equilibrium but no forces are required on A to hold it straight?
12. (Original post by alesha98)
A goes up, B goes down. i think i get it, so when the weight on B is maximum, the tension in A is 0 because although the beam remain in equilibrium but no forces are required on A to hold it straight?
Correct
13. (Original post by ghostwalker)
In this case you have three unknowns and effectively only two equations, since the third can be derived from the other two (hence dependent). And that's not enough to solve the system of equations.
Thankyou , i understand what it means by maximum weight at B and i know how to approach this kind of questions now.

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