centripetal-forcenewtonian-mechanics
This experiment is shown in my book.
The book says 'a mass of weight 1.0N is attached on the nylon thread. This creates a centripetal force F of 1.0N on the bung.'
However, isn't there a component of the rubber bung also contribute to the tension and therefore the centripetal force?
You have to consider the two axes separately: lets call $x$ the horizontal plane, and $y$ the up and down (direction in which gravity acts). In the "free-body diagram" of the ball, there are also three forces to consider: 1) gravity, 2) centripetal, and 3) the tension in the string. The tension in the string needs to balance the combination of gravity and centripetal acceleration.
The centripetal acceleration itself, has nothing to do with gravity, it only has to do with the ball's circular motion. Instead of the ball spinning nearly-horizontally, you can imagine spinning it ever so slowly---and it remaining nearly vertical. Gravity hasn't changes, only the centripetal acceleration, and thus tension in the string---via force balance in the $x$ direction.
Because there is gravity in the $y$ direction, the string can never be fully horizontal, because some amount of the string tension must act in the $+y$ direction to counteract gravity. Thus, only the $y$ component of the string-tension is determined by gravity, and this occurs regardless of the centripetal force.
For equilibrium, the horizontal string has really to be at an angle $\theta$ as shown in the diagram.
Then resolving forces vertically on the large mass, $T=Mg$
the centripetal force is from $T\cos\theta$
and the small mass is supported by the vertical component of the tension $T\sin\theta$
Best Answer
Indeed it does! The tension in the thread is affected both by the weight of the central mass and by the weight of the rubber bung; as you spin the rubber bung faster, the tension in the rope on the bung end tilts further and further askew from the direction of gravity, meaning the tension must grow larger so that its vertical component balances gravity. This is happily in line with physical intuition.