While motorcyclists frequently ride at speeds higher than 20 m / s ( 45 mph ), the perpendicular impact speed of the helmet is usually not the same as the road speed of the motorcycle, and the severity of the impact is determined not only by the speed of the head but also by the surface it hits and the angle of impact.
42.
A ratio of 2 between caliber and penetration was good by World War II standards and is explained by the late design and lack of penetration degrading spin ( the 10H64 had a smoothbore barrel and fin stabilized shells ) . 200mm penetration would have been enough to defeat all existing tanks of World War II unless the angle of impact prevented proper fusing.
