A stone of mass m attached to a string of length l is whirled in a...

When a stone of mass $m$ is whirled in a circular path of radius $l$ with speed $v$, its velocity at any instant is directed along the tangent to the circle at that point. The centripetal force required for circular motion is provided by the tension in the string.

If the string breaks, the tension becomes zero and the centripetal force vanishes.

According to Newton's first law of motion, in the absence of any external force, the stone will continue to move in the direction of its instantaneous velocity.

Therefore, the stone will travel along a tangent to the circular path.