The trucks gain/gather 'speed' as they drive down the hill. = The trucks pick up 'speed' as they drive down the hill. [=the trucks go faster as they drive down the hill]
He types at a 'speed' of about 50 words per minute. = His typing 'speed' is about 50 words per minute.
Let me 'bring you up to speed' on our plans. [=let me tell you about the changes in our plans]
(..) Tasty, isn't it? Gonna have to pick tooth. Now? Now. Please save me. I wanna hit him full speed. That's okay, Frank. We'll have some fun with him . Don't let them kill me, please. I wanna live! Get off me! Come on, you're making a scene. We just take off free and go. Do your mind? (..)2002 Ice Age