hi there! I considered the following problem: a ball of radius R on a horizontal plain is at first in rest. Then it receives a horizontal force for a very short time at a point placed 1/3R from the plain and the ball starts moving with initial velocity v_0. There is also a friction when the ball slides. the question is: at which velocity v will the ball start rolling? here´s what I figured out: the force initiates a torque such that the ball gets initial angular velocity w_0, counter clockwise. But the velocity v initiates another angular velocity w in clockwise direction. My assumption is that the ball will start rolling counter clockwise when the velocity v becomes 0. what do you think?