Re: Sin PHYSICS
You can drop items you have picked up by simply pressing use again. This will cause them to fall straight down from your hand. When throwing an item, it throws it based on where you picked it up. So if you pick up a health canister on the end and throw it, it will flip around more than if you pick it up in the middle.
Things like not being able to get over fences or cars have nothing to do with the main storyline in the game - ergo they are not indicative of anyone's skill if you simply cannot cross them. Those are there to prevent you from getting outside the game world. In order to prevent the player being able to jump somewhere and get stuck/not be able to jump back, we have chosen to block the player from being able to get to that area.
I'm sorry if these issues are hindering your enjoyment of the game, but they are fairly common even in games such as Half-Life 2.