1. The problem statement, all variables and given/known data A small container of water is placed on a turntable inside a microwave oven, at a radius of 12.0 cm from the center. The turntable rotates steadily, turning one revolution in each 7.25 s. What angle does the water surface make with the horizontal? 2. Relevant equations F = ma a = v^2/ r 3. The attempt at a solution Find the velocity of rotation: 0.12 x 2 x pi/ 7.25= 0.1 m/s Find the centripetal acceleration: (0.1)^2/ 0.12 = 0.09 ms^-2 Centripetal acceleration = 0.09 ms^-2 = horizontal acceleration Gravitational acceleration = 9.8 ms^-2 = vertical acceleration Angle make wit the horizontal surface arctan (9.8/0.09) = 89 degree I know it should have been arctan (0.09/9.8) = 0.526 degree (the actual answer), but in this way the centripetal acceleration would become the vertical acceleration whereas the gravitational acceleration would become horizontal acceleration. What's wrong? Thanks!