When bod is whirled into a vertical circle. The required centripetal force is obtained from the tension in the string. When string is cut, tension is string is cut, tension is string becomes zero and centripetal force is not provided, hence bob start to move in a straight line path along the direction of its velcity
(a) At point B, the velocity downward, therefore, when string is cut at B, bob moves vertically downward.
(b) At point C, the velocity is along the horizontal towards light, thererfore, when string is cut at C, bob moves horizontally towards right. Also, the bob moves under gravity simultaneously with horizontal uniform speed. So, it traversed on a parabolic bpath with vertex at C.
(c ) At point X, the velocity of the bob is along the tangent drawn at point X, therefore when string is cut at poitn C, bob moves along the tangent at that point X. Also, the bob move under th agravity simultaneously with horizontal uniform speed. So, it traversed on a parabolic path with vertex higher than C.
