Answer:
960 N
Explanation:
answer should have two signif digits Â
a = change in velocity divided by change in time
  1 m/s / .5 s =  2 m/s^2
F = ma    a = g + 2 m/s^2 = 9.81 + 2 =  11.81 m/s^2
 81 kg * 11.81 m/s^2  = 956.61  N = ~ 960 N  (two sig digits)
(Please let me know if this is incorrect....I am not SURE )