# some doubts regarding rotational dynamics

by dreamz25
Tags: doubts, dynamics, rotational
 P: 26 a) suppose we tie a ball with a string and rotate it keeping its other end tied with one of our fingers then the only external force acting on it is the tension. Which force then cancells 'mg' acting vertically downward? b) if a mass is rotating in a circular path then in which direction does the net external force acting on it acts?
Mentor
P: 40,264
 Quote by dreamz25 a) suppose we tie a ball with a string and rotate it keeping its other end tied with one of our fingers then the only external force acting on it is the tension. Which force then cancells 'mg' acting vertically downward?
Not exactly sure what you are describing. But if you twirl the ball on the end of a string in a horizontal circle, the string will make an angle with the horizontal. The net vertical force will be zero.
 b) if a mass is rotating in a circular path then in which direction does the net external force acting on it acts?
What do you think?

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