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Will a ball which is connected to a pivot through a massless string keep revolving after it is made to perform uniform circular motion? What will be the role of tension in it? Will it (tension) draw the ball towards the centre, or will it provide the centeipetal force? If tension indeed acts then is there a force that balances it?

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  • $\begingroup$ In the absence of friction it will keep revolving for all of eternity.In reality that doesn't happen, of course. $\endgroup$
    – Gert
    Commented Apr 13, 2020 at 20:51
  • $\begingroup$ What role does the tension will play in it? $\endgroup$
    – Eyy boss
    Commented Apr 13, 2020 at 21:02
  • $\begingroup$ The horizontal component of the tension provides the centripetal force, needed to keep the ball on its circular trajectory. $\endgroup$
    – Gert
    Commented Apr 13, 2020 at 21:36

2 Answers 2

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An easy way to think of tension is that it would be the sum of forces required to keep the rope at the same distance from the pivot as it was. In this case the tension should be equal to the centripetal force. Here are some cases to consider,

if, $$ T - mw^2 r \geq 0$$ then, the object would accelerate inwards and

if, $$ T-mw^2 r \leq 0 $$ the object would accelerate outwards

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The tension keeps the ball from flying off in a straight line in some direction. You could think of tension like the effect the sun's gravity has on the earth- it keeps it in orbit.

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  • $\begingroup$ the 'stupid' refers to me, not you... $\endgroup$ Commented Apr 13, 2020 at 21:17

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