if a mass of 50kg moves a velocity of 35km|hr calculate the time taken to bring it to rest by a constant force of 100newton

Vi = 35,000 m / 3,600 s = 9.72 m/s

F = m a
-100 = 50 a
a = -2 m/s^2
0 = Vi + a t
0 = 9.72 - 2 t
t = 9.72/2