Question

If the angular momentum is conserved is the torque present???

Answer 1

No, by definition\[\tau = {dL \over dt}\]

Answer 2

then if the anguar momentum isnt conserved the torque is present right??

Answer 3

Correct.

Answer 4

http://www.youtube.com/watch?v=4u7OwGkWqrk&feature=related
in this example is the angular momentum being conserved or not??

Answer 5

No. The candle swings due a change in mass on either side of the pivot point. Gravity acts upon the mass to create a torque. Here is an example of conservation of angular momentum: http://www.youtube.com/watch?v=MjYk5TRpOlE

Notice how his angular velocity increases when he tucks his hands in close to the body? This is due to a decrease in the moment of inertia of the body. Remember that \[L = I \omega\]
As \(I\) decreases, \(\omega\) must increase such that L remains constant.