Question

The use of the arm in an almost fully extended position increases the length of the lever, thereby giving greater linear velocity to the racket head than would be the case if the upper arm were close to the body. This is only true however, if the racket can be moved with the same angular velocity in oth positons.

next question

The effort needed to resist the force of the ball hitting the racket is less when the racket arm is shortended.

Answer 1

for first question because we have that the linear velocity v=rw where w is angular velocity, the velocity is more at extended position due to a higher value of r, the radius (with angular velocity remaining same in both instants)

now for second question as from the above the linear velocity is more for more radius so the change in momentum due to a ball hitting a racket with same velocity will be more at extended position as the angular velocity generated remains same in both conditions but the radius is less when racket arm is shortened, so due to lesser change in momentum we need lesser effort for shortened racket arm