time bullet physics, eg. ball drop?

Hi all I’m new to the BGE and just want to use it to add some bullet physics. How do I, for example, make a ball start dropping at say frame #50?

(using 2.5, recent trunk svn’s)

What do you mean by frame #50? If you want a ball do stop dropping after a delay of some kind, hook up a delay sensor to an edit object actuator set to “enable rigid body.”