Yes, a ball must be kicked forward at a penalty kick in soccer.
When a football is kicked, some of the force is absorbed by the football, and any force remaining is transferred in propulsion of the football forward.
The ball is in play when it is kicked and moves. The movement does not have to be forward.
it has to be kicked forward
No, rugby doesn't have a wide receiver; that's more an American football term and in that game the ball can be thrown forward or kicked forward. In rugby (both codes), the ball can be kicked forward and passed laterally or behind the ball carrier only
The ball moves in the direction you kicked it.
It means the ball was hit (kicked) hard and straight forward.
when a soccer ball is kicked, there is a transfer of energy from your leg to the ball. since the ball is elastic, it coverts the kinetic energy from your leg into potential elastic energy in the for of deformation of the ball. the ball then snaps back to its elastic equilibrium converting the energy back to kinetic energy. also, your momentum is being transferred to the ball, giving it a direction since momentum is a vector. due to these conversions of energy and momentum, the ball is sent off your foot in the direction you kicked it with the same speed you kicked it with.
The ball must be passed either in line with the ball carrier OR as is normally seen to the rear of the ball carrier. A ball thrown forward, dropped forward of the carrier or knocked forward of the ball carrier is a penalty offense
The ball must move forward on the initial kick. Forward is "towards the opponent's goal line."