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# Tension in a light inextensible string M1 watch

1. Hi,
Basically on a past paper questions I am doing the question says:
Smooth bead B, is threaded on a light inextensible string. The end of the string attached to two fixed points A and C on the same horizontal level. The bead is held in equilibrium by horizontal force of magnitude 6N acting parallel to AC. The bead B is vertically below C and Angle BAC = a. Given that tana = 3/4. Find the tension in the string.

Please can someone highlight to me which of this wording allows me to presume that the tension is the same in both parts of the string.

Is it the wording ‘ light inextensible string’? As I have presumed when doing my working I can see no other way to work this one out.

Regards.
2. (Original post by usuallymathshelp)
Hi,
Basically on a past paper questions I am doing the question says:
Smooth bead B, is threaded on a light inextensible string. The end of the string attached to two fixed points A and C on the same horizontal level. The bead is held in equilibrium by horizontal force of magnitude 6N acting parallel to AC. The bead B is vertically below C and Angle BAC = a. Given that tana = 3/4. Find the tension in the string.

Please can someone highlight to me which of this wording allows me to presume that the tension is the same in both parts of the string.

Is it the wording ‘ light inextensible string’? As I have presumed when doing my working I can see no other way to work this one out.

Regards.
The bead is threaded on the string - i.e. not fixed - and the bead is smooth.

These tell you the tension is the same in both parts.
3. (Original post by ghostwalker)
The bead is threaded on the string - i.e. not fixed - and the bead is smooth.

These tell you the tension is the same in both parts.
Thank you. Please could you explain why because I thought that being smooth simply meant there was no friction. Thank you for your help.
4. (Original post by usuallymathshelp)
Thank you. Please could you explain why because I thought that being smooth simply meant there was no friction. Thank you for your help.
Being smooth does mean there is no friction.

How can the tension be different in the two parts? By a force acting along the string. Where would that force come from? Friction, or the bead being fixed to the string and pulled.

So, not fixed and smooth implies tension is the same in both parts.

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