A rod of mass m and length l is lying on a horizontal table. The work done in making it stand vertically on one end will be
As shown in fig, a bob of mass ‘m’ is attached by one end of string of length 1 metre and makes an angle 60∘ with vertical. When it is released it strikes perfectly elastically with block of mass ‘3m’ (which is rest on smooth horizontal table). The height of table is also 1 metre. The range obtained by ‘3m’ block from vertical side ‘CD’ of table will be…………….