Answer :
F= ma
31-mg = m(-2.5m/s2)
31= mg-2.5 m
31 = m*(9.8m/s2 -2.5 m/s2)
31 = 7.3 m
m = 31/7.3
m = 4.25 kg
31-mg = m(-2.5m/s2)
31= mg-2.5 m
31 = m*(9.8m/s2 -2.5 m/s2)
31 = 7.3 m
m = 31/7.3
m = 4.25 kg