A truck starts from rest with a constant acceleration. During the 5th second it covers a distance of 10m. What is its acceleration?

Let us define some parameters, 

let, s- distance.

a - acceleration.

t - time

u - initial speed

In 4 seconds, the truck covers a distance of. 

s = ut + 1/2 (at²)

u= 0 (given) 

s = 1/2 (a 4^2)

s = 1/2 (16a)

s = 8a meters

and,

In 5 seconds, the truck covers a distance of, 

s = ut + 1/2 (at²)

s = 1/2 (a 5^2)

s = 1/2 (25a)

s = 12.5a meters

The distance covered in 5 seconds - the distance covered in 4 seconds = the distance covered in the 5th second.

10 = 12.5a - 8a

10 = 4.5a

a = acceleration = 2.22 m/s²