Function SetVehicleVelocity sets the X, Y and Z velocity of a vehicle.
Function SetVehicleVelocity was added in 0.3a and will not work in earlier versions!
This function has no affect on un-occupied vehicles and does not affect trains.

(vehicleid, Float:X, Float:Y, Float:Z)
int vehicleid The ID of the vehicle to set the velocity of.
float X The velocity in the X direction.
float Y The velocity in the Y direction.
float Z The velocity in the Z direction.

Return Values:
  • 1: The function was executed successfully.
  • 0: The function failed to execute. The vehicle does not exist.

public OnPlayerCommandText(playerid, cmdtext[])
    if (!strcmp("/jump", cmdtext))
        SetVehicleVelocity(GetPlayerVehicleID(playerid), 0.0, 0.0, 0.2);
	return 1;

Related Functions
The following functions may be useful, as they are related to this function in one way or another.