djemix Jul 27, 2011 at 12:14 PM Edited Jul 27, 2011 at 12:20 PM Hello! I'll try to explain my trouble, my english is very poor. I'm doing a game in WP7 using Farseer physics, it's a basketball game. My trouble is that the move of the ball is very slow when the gravity act in it. I have a world created like this: ```world = new World(new Vector2(0f, 20f)); ``` And then, in update method: ```world.Step(Math.Min((float)gameTime.ElapsedGameTime.TotalSeconds, (1f / 30f))); ``` I've the ball created like this: ```body = BodyFactory.CreateCircle(world, 17, 1f); body.CreateFixture(new PolygonShape(PolygonTools.CreateCircle(17, 10), 1f)); body.BodyType = BodyType.Dynamic; body.Restitution = 0.8f; ``` And then, when I want to throw the ball I do: ```body.ApplyForce(new Vector2(100000000000, -100000000000)); ``` Why the ball is very very slow movement? Only I do the ApplyForce once time when I want to throw the ball, is correct? Or I'va to ApplyForce in loop update? And if I don't applyForce for that only act the gravity, it's the same that I put 20f that 2000f to the vector gravity, the ball down at the same velocity.   Thanks for all! body.ApplyForce(new Vector2(100000000000, -100000000000)); des91iraq Jul 27, 2011 at 6:22 PM hey man   Iam new here :)   I think your problem in World.Step()   the argument I have in C# is   world.Step((float)gameTime.ElapsedGameTime.TotalMilliseconds * 0.001f ); converting the number returned from  TotalMilliseconds to seconds :) gjwebber Jul 28, 2011 at 7:12 AM I don't think you need to create a new fixture for the body, BodyFactory already does this for you. The slow movement may be down to the scale of things. You have created a ball with a 17 meter radius... that's a pretty big ball to be throwing. Take a look at the samples and use the ConvertUnits.ToSimUnits() method maybe? djemix Jul 28, 2011 at 6:55 PM It's perfect gjwebber. Now work perfectly. I have another cuestion. How can I calculate the Vector2 to the ApplyLinearImpulse if I have the power and the angle? danwieder Jul 30, 2011 at 4:24 AM This should work. Vector2 i =  Vector2(cos(angle), sin(angle)) * power;