Question

any one who can solve........

Answer 1

m = 140 gm = 0.14 kg ,v1 = 39 m/s ,v2 = -39 m/s
F = m(v1 - v2)/∆t
   = 0.14[39 -(-39)] / (1.2 x 10^-3)
   = 1400 x 78 / 12
   = 9100 N

i hope it will help you
regards