The initial velocity of the truck (u) = 0 (As the truck is initially at rest)
Distance covered (s) = 400 m,
Time (t) = 20 sec
Mass of the truck (m)
= 7 metric tonnes = 7 x 1000
= 7000 kg
To find: Acceleration (a) = ?
Force (F) = ?
Using second equation of motion
S = ut + \(\frac{1}{2}\) at
400 = 0 x 20 + \(\frac{1}{2}\) x a x (20)2
⇒ 400 = \(\frac{1}{2}\) x a x 400
⇒ a = 2m/s2
Now F = ma = 7000 x 2
= 14000 kgm/s2 = 14000 Newton