Speed of ball changed by lengthening string

  • Thread starter fattydq
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  • #1
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A ball of mass 0.18 kg is whirled in a horizontal circle at the end of a massless string 75 cm long at a speed of 4.5 m/s. If the string is lengthened to 1.5 m while the ball is being twirled, then the speed of the ball will now be...

What law or formula applies to this question?
 

Answers and Replies

  • #2
ideasrule
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I think you're supposed to assume that external torque is 0, so the conservation law is...
 

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