A tackle in rugby is much different than any other sport. The tackler wants to wrap up around the upper legs, dragging the runner to the ground to force a turnover. By wrapping the legs, the forward momentum of the player with the ball takes them to the ground. Momentum measures how hard it is to stop moving an object. A rugby player, like a football player, hits at the low because a runner's mass is concentrated at the center. The momentum is conserved. An elastic collision is just like a rugby tackle because the momentum is equal before and after. The ball is thrown underhand. The thrower decides the angle in which the ball is thrown and distance and speed but the height usually remains constant. There are so many lineouts in rugby but they are pretty self explanatory.