Kronwall is one of my favorite defenseman in the NHL. The reason for this being his huge hits that he has (shown below) and this great defensive play. The reason for hit great hits is because he combines his massive self with a good amount of speed to completely wreck players. The main reason this is so effective is because of a fundamental aspect of physics which is the idea that momentum must be conserved. Since he catches his opponent off guard it allows him to build speed and use his mass to collide with the other played and cause for him to continue on in his original direction. Even though his speed gets slowed significantly from this it is because he has just collided with another massive player. But, since he has more speed and a better center of mass this opponent gets "Kronwalled"