The LAW in real life is an antitank rifle, use to damage or take out tanks in urban or close environments, allowing them to be discarded after use.
The RPG-7 is a grenade launcher (rocket propelled grenade) small blast damage but more damage because of the small focus area, the grenade is able to bounce off ground and therefore, if you have a loaded RPG-7 (lets say you can't be killed). If you aim it at the ground, it does not often explode on contact, it bounces off. You can use a spring mattress on your tank and it'll bounce off and do little or no damage. The grenade in the RPG is a timer, once the timer kicks in, the RPG will explode onto contact.