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# M1 understanding tension. watch

1. I can never tell which direction the arrow is going to be going in on the string, and consequently i am unable to resolve the forces, how do you know which direction the arrows on the string (to indicate tension) will be? Especial in cases of pulleys and inclined planes. Thank you.
2. (Original post by Core)
I can never tell which direction the arrow is going to be going in on the string, and consequently i am unable to resolve the forces, how do you know which direction the arrows on the string (to indicate tension) will be? Especial in cases of pulleys and inclined planes. Thank you.
I can send you a couple of Powerpoints that might help if you pm me with an email address.

Tension always points into the centre of the string from both ends.
3. i usually just think of tension as going away from something, like with pulleys, the arrow will be going away from it, and then with the particles attached to the pulleys, the arrow for their tension will be going away from them (and towards the pulley), hope this helps, sorry if its a bit confusing
4. Towards the thing holding it in place, so if you have a smooth pulley with a light inextensible string going over it, there will be two (equal) tensions to put on, one on the horizontal part of the string going towards the pulley, and one on the vertical bit of the string (the one hanging, usually holding a weight) also going towards the pulley.
5. I have had cases were there were four arrows, and then 2 arrows. Its abit confusing because the case in which there were four arrows as on an inclined plane but there were also 2 arrows in another case on an inclined plane. Then there was another case where a pan was being raised and the arrow was going upwards on the string.

Actualy the case with 4 arrows was when 1 particle was on a horizontal plane and the other was hanging off the edge, the string was on a pulley in this case also
6. (Original post by Core)
I have had cases were there were four arrows, and then 2 arrows. Its abit confusing because the case in which there were four arrows as on an inclined plane but there were also 2 arrows in another case on an inclined plane. Then there was another case where a pan was being raised and the arrow was going upwards on the string.
There are only ever two arrows on each string that represent tension. The other arrows must be other forces.
7. There was a case where two particles dangled from a pulley and there were four arrows labled T
8. (Original post by Core)
There was a case where two particles dangled from a pulley and there were four arrows labled T
Then the tension is directed towards the pulley
9. (Original post by Core)
There was a case where two particles dangled from a pulley and there were four arrows labled T
Eh? You drew that incorrectly I suspect.
10. (Original post by kashim91)
Then the tension is directed towards the pulley
two faced the particles and 2 faced the pulley, Im not really sure how this tension force works. Is the tension lifting the particles up and pulling the pulley down?
11. (Original post by Mr M)
Eh?
The string went around the pulley and on each side of the pulley was a particle with a different mass to its opposite particle. When the system was released from rest on particle descended as the other ascended
12. (Original post by Core)
The string went around the pulley and on each side of the pulley was a particle with a different mass to its opposite particle.
There should have been two arrows marked T, one on each side of the pulley pointing towards the centre of the string. Any arrows pointing down would have been the weights of the particles. I have already offered you Powerpoints on this topic.
13. (Original post by Mr M)
There should have been two arrows marked T, one on each side of the pulley pointing towards the centre of the string. Any arrows pointing down would have been the weights of the particles. I have already offered you Powerpoints on this topic.
Thanks Il pm you.

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