Answer:
The value is 
Explanation:
Generally the relative speed at which you are moving with respect to the person ahead of you is mathematically represented as
substituting 1.05 m/s for 
and 2.75 m/s for 
So
=> 
Generally the distance by which the person is ahead of you is mathematically represented as
substituting 18.5 s for 
=>
Answer:
The downward force of gravity and the force exerted by the air.
Explanation:
Gravity, in a Newtonian Framework, acts at distance, so, the ball doesn't has to be connected to Earth to feel its gravitational pull (as we know by experience).
The racket only can exert a force in the ball when is touching it, so, once the ball has left the contact with the racket, there is no force by the "hit".
The air is always touching the ball on the atmosphere (even when physicist pretend that is not). So, there is drag from the wind, and a buoyant force exerted by the air over the ball at every time.
