Why we need to use 24 frames for a second in animation

In video technology, 24p refers to a video format that operates at 24 frames per second (or typically, 23.976frame/s when using equipment based around NTSC frame rates) frame rate with progressive scanning (not interlaced). Originally, 24p was used in the non-linear editing of film-originated material. Today, 24p formats are being increasingly used for aesthetic reasons in image acquisition, delivering film-like motion characteristics. Some vendors advertise 24p products as a cheaper alternative to film acquisition.
When working entirely within the digital non-linear domain, 24p material is as easily handled as material at any other frame rate. However, 24p material requires care when it is processed using equipment designed for standard video frame rates.
There are two common workflows for processing 24p material using video equipment, one using PAL frame rates, and the other using NTSC frame rates. Of these two, the PAL route is the simpler, but each has its own complications.