If the footballer kicks the ball in north east direction the force wich is given is in north rast direction .         ( The vector quantity is those physical quantity wich require magnitude as well as direction for their complete representation & follows vector laws are called vectors). This way of applying force cause parabolic motion to the ball . Wich means the ball makes an arc in space.
Now look at a small instant of time to the ball while it is moving up .NOTE: In physics most of the physical quantity is told is with respect to an body. Take an example if you kick a football parallel to the ground with respect to you let the ball moves 10 km/hour  because of your force. Consider a boy is running  5km/hr in the direction you kicked the ball . With respect to him the ball is moving 10 – 5= 5km/h . This is called relative velocity . This topic will be studied in XI . Now in our topic if the ball is moving upward with a velocity (a vector) . Take a small interval of observation the ball will displace upward and also in horizontal with respect to you . (The reason for saying with respect to a body is that for another person the velocity is reduced or increased or zero.The velocity wich you observe is not experienced by another body ) You can split the velocity of the ball into two , this is call reselution of a vector (the force wich the kicker applied can be divided into two direction. Remember that force is vector the force kicker give to the body is saved as  energy this energy is spending or converting during it motion ) .

       The force (vector) wich the kicker applided on the ball cause the ball move in upward direction with respect to the kicker is called as the vertical component. This component of force is not constant throught the motion of the ball. This will be get reduced by the cause of gravitational force due to earth on the body. The point at wich the vertical component of force becomes zero (wich means the body don’t move up after that point ). The given energy to the ball is stored as potential energy of the ball ( mgh) . Due to the cause of further attraction by gravity the ball get accelerated downwards(wich means that there is no vertical component force given by the kicker to over come the gravitational attractional force) . The dicection wich the kicker kicks the ball is north-east direction with respect to the earth . This cause the body have a horizontal vector in derection to north east direction. Where this force causing the body to displace in horizontal direction will be a constant through out the motion . This is because there is no air resistence & according to the  Newton‘s first law of motion “ Every body continues in state of rest or in uniform motion until an external unbalence force acts on it”. I this horizontal motion There is no external un balence force aganist this force. Thus the horizontal velocity is constant througt the motion if neglecting the air resistence. But in case of vertical component there is an external unbalence force acting in opposite diection thus the velocity reduces to zero(Here retadation or deacceleration or -ve acceleration takes place when the ball is moving up ward)  Then the potential energy is converted into kinetic energy( It follows the laws of conservation of energy). At last the ball toches the ground the energy given by the kicker to the ball is transfered to the ground (May be in form of heat energy),air ( as sound energy) etc. Then the cycle goes on …...

Remember “  The total amout of matter and energy avilable in the universe is fixed”

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Remember the words said by A.P.J Abdul kalam

                 “Keep asking questions till you get satisfactory answers”