[填空题]
A 0.145-kg baseball pitchexe,r v 8.wp mab4/+uhg02fuimzrn2c jh b,. .nd at 39 m/s is hit on a horizontala: b imv (v(z+xc 32-dd;zdnbv line drive straight back toward ddb;c:d -vv( a+3z(n x2mi bvzthe pitcher at 52m/s If the contact time between bat and ball is $3\times10^{-3}$s calculate the average force between the ball and bat during contact. N
