SpriteKit Obj-C – How to add a force on a node a certain distance according to screen size

I have an SKSpriteNode that I'm trying to throw up to a certain point on the screen. I've tried applying an impulse and/or force according to the screen size, but that has strange results. I've also tried changing the sprite's velocity according to the screen size. Here's some code I tried.

- (void)createFlyingButton
{
NSLog(@"Flying button created!");

// Create the button.
SKSpriteNode *button = [SKSpriteNode spriteNodeWithImageNamed:@"BlueButton"];
button.name = @"BlueButton";
button.size = _buttonSize;
button.position = CGPointMake(randomInRange(self.size.width * 0.25, self.size.width * 0.75),
-(_buttonSize.height * 3.0));
button.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:_buttonSize.width * 0.5];