A uniform thin rod of mass M and length L is standing vertically along the y-axis on a smooth horizontal surface, with its lower end at the origin (0,0). A slight disturbance at t = 0 causes the lower end to slip on the smooth surface along the positive x-axis and the rod starts falling. The acceleration vector of centre of mass of the rod during its fall is[¯R is reaction from surface]
a. ¯aCM = M¯g+¯R/M
b. ¯aCM = M¯g−¯R/M
c. ¯a = M¯g+¯R
d. None of these