A 1000 Kgs Vehicle moving with a sppeed of 20 meter per sec. is brought to rest in a distance of 50 metres. find the acceleration

Vf^2 = Vo^2 = + 2ad,

a = (Vf^2-Vo^2) / 2d,
a = (0-(20)^2) / 100 = -4m/s^2.