Answer:
acceleraions 5.76g and 20.55g
Explanation:
This constant acceleration exercise can be solved using the kinematic equations in one dimension
  Vf = Vo + a t
As part of the rest Vo = 0
  a = Vf / t
  a = 282/5
  a = 56.4 m / s2
In relation to the acceleration of gravity
  a ’= a / g = 56.4 / 9.8
  a ’= 5.76g
To calculate the acceleration to stop we use the same formula
   a2 = 282 / 1.40
   a2 = 201.4 m / s2
 This acceleration of gravity acceleration function is
   a2 ’= 201.4 / 9.8
   a2 ’= 20.55g