[Extricated]

http://www.xtremepapers.com/papers/E...%202004-01.pdf


Question 4, part b. Why is tension acting downwards i.e the tsintheta component? I thought it would be acting upwards??

[raheem94]

(Original post by Extricated)
http://www.xtremepapers.com/papers/E...%202004-01.pdf


Question 4, part b. Why is tension acting downwards i.e the tsintheta component? I thought it would be acting upwards??

See the diagram below:



The tension is in both directions.

When we resolve forces on particle A, we consider the red tension, while when we resolve forces on particle B, we consider the blue tension.

In your question the tensions act like this,




Hope it makes sense.

[Extricated]

(Original post by raheem94)
See the diagram below:



The tension is in both directions.

When we resolve forces on particle A, we consider the red tension, while when we resolve forces on particle B, we consider the blue tension.

In your question the tensions act like this,






Hope it makes sense.

Thanks raheem,

but why do we consider the red tension on A and blue on B? Also, where are there two tensions, normally there's only 1?

[raheem94]

(Original post by Extricated)
Thanks raheem,

but why do we consider the red tension on A and blue on B? Also, where are there two tensions, normally there's only 1?

Tensions act on both particles, their magnitude is same.

Just have a look here.

[physicsdoc]

The quick answer is the string is attached to two objects.

Throughout Mechanics, resolving forces is the key.

One of the (tension) forces is due to A on C and the other is due to C on A (the same applies for B on C and C on B). For a system in equilibrium the two tensions are the same (and act in opposite directions). This stems from Newton's 3rd Law. Hope that clears it up.