A ball tied to the end of a string 0.50 m in length swings in a vertical circle under the influence of gravity. When the string makes an angle x= 20 degrees with the vertical, the ball has a speed of 1.5 m/s. Find the magnitude of the radial component of acceleration at this instant. So i have a concept question. How do i know that tangential acceleration = gsin(20 degrees). Basically, prove the general formula tangential acceleration= gsin(x) for this problem.