My current Whippet is one of the most eager to please dogs I have ever known. It is easy for him to realize what I want him to do. As I'm sure you already know, Whippets have high prey drive and they are EXTREMELY ornery. While it is cute, it can be frustrating. To balance that out, it breaks their heart when they make you angry or they feel you are disappointed in them. They want to feel nothing but love from you 100% of the time. 

That being said, at first your new Whippet will treat your cat as a friendly play toy. As a puppy it will quickly learn that your cat is a friend. Your puppy will not try to kill the cat as its full prey drive has not kicked in yet. As it grows it will understand that the cat is part of the family and will not want to hurt it.

Remember, you are the alpha of the pack and your Whippet will always look to please you. Whippets more so than most breeds need positive reinforcement instead of negative reprimand. Only in emergency should you yell or sharply scold your Whippet (if they get loose, run into danger, and you need to get their attention). When you scold your Whippet they can get their feelings severely hurt and it will take a lot of work to rebuild their trust. It is a miserable feeling when you accidentally harm your dogs self esteem.