# Why are the tensions the same for BC and BD?Watch

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Thread starter 1 year ago
#1

iii) Why are the tensions the same for BC and BD?
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1 year ago
#2
They are at the same angle to the vertical and experience the same force.
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Thread starter 1 year ago
#3
(Original post by BTAnonymous)
They are at the same angle to the horizontal and experience the same force.
Thanks
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Thread starter 1 year ago
#4
(Original post by BTAnonymous)
They are at the same angle to the vertical and experience the same force.
Actually why does the angle to the vertical affect the tension - I thought it only affected vertical and horizontal components of the tension.

This is what you kindly advised today with one of my other questions "the tension doesn't change but the VERTICAL COMPONENT OF THE TENSION must change if the angle changes."
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1 year ago
#5
(Original post by h26)
Actually why does the angle to the vertical affect the tension - I thought it only affected vertical and horizontal components of the tension.

This is what you kindly advised today with one of my other questions "the tension doesn't change but the VERTICAL COMPONENT OF THE TENSION must change if the angle changes."
In this case the vertical component must be constant, so the result force (the tension in BD or BC) changes to ensure the vertical component is constant. The vertical component in each string is equal to the tension in the light string.

In the other case, the resultant must of remained constant, so to ensure the result was constant when the angle changed, the horizontal and vertical changed correspondingly.
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1 year ago
#6
Well you can see that the whole system is in equilibrium, which means there are no unbalanced forces. Therefore B/C and B/D must be the same, right?
also it looks like an Isosceles triangle XD
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Thread starter 1 year ago
#7
(Original post by BTAnonymous)
In this case the vertical component must be constant, so the result force (the tension in BD or BC) changes to ensure the vertical component is constant. The vertical component in each string is equal to the tension in the light string.

In the other case, the resultant must of remained constant, so to ensure the result was constant when the angle changed, the horizontal and vertical changed correspondingly.
Isn't it the vertical component in each string combined that is equal to the tension in the light string though?
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1 year ago
#8
(Original post by h26)
Isn't it the vertical component in each string combined that is equal to the tension in the light string though?
Yes sorry, the sum of the vertical components in each string must be the sum of the tension in the string as the system is in equilibrium.
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Thread starter 1 year ago
#9
(Original post by BTAnonymous)
In this case the vertical component must be constant, so the result force (the tension in BD or BC) changes to ensure the vertical component is constant. The vertical component in each string is equal to the tension in the light string.

In the other case, the resultant must of remained constant, so to ensure the result was constant when the angle changed, the horizontal and vertical changed correspondingly.
For the question here
Why do the vertical components of B and C have to be the same in order to cancel out the tension in the light string? I mean say the tension in the light string is 5N, vertical component of BC can equal 3N and vertical component of BD can equal 2N which combined cancel out the tension in the light string
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1 year ago
#10
If you consider the net *horizontal* force at B, it's immediate that the tension in the two strings must be equal.
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