Can anyone help me with this part of the game. Need a sprite to free fall after a button is pressed.

[StephenDunne]

  This is a group of sprites , I want the num1 sprite to free fall from the ship when The spacebar is pressed.

 

ufo = game.add.group();

    xray = ufo.create(732, 210, 'xray');

    ship = ufo.create(700, 175, 'sprite');

    num1 = ufo.create(718, 290, 'number1');

 

 

 

 

else if (dropButton.isDown)

{
//Move down
num1.body.velocity.y = 900;
xray.destroy;
}

 

 

When the drop button is pressed the sprite moves down the screen and is still connected to the ship. But what I want is for the sprite to free fall. Is there any documentation I can look at regarding this? Any working examples of a sprite in free fall after a button event?