A truck starts from rest and rolls down a hill with a constant acceleration. It travels a distance of 400 m in 20 s. Find its acceleration. Find the force acting on it if its mass is 7 metric tonnes (Hint: 1 metric tonne = 1000 kg.)

– Distance traveled by the truck (s) = 400 m
– Time taken (t) = 20 s
– Mass of the truck (m) = 7 metric tonnes = 7,000 kg (as 1 metric tonne = 1000 kg)

Calculating Acceleration:
We’ll use the kinematic equation ( s = ut + 1/2 at²), where (u) is the initial velocity (which is 0 m/s as the truck starts from rest).

s = ut + 1/2 at²
400 = 0 x 20 + 1/2 x a x 20²
400 = 200a
a = 400/200
a = 2m/s²

Calculating Force:
Now, using Newton’s second law of motion F = ma :

Given:
– Mass m = 7000 kg
– Acceleration (a) = 2 m/s²

F = ma
F = 7000 x 2
F = 14,000 N

Conclusion:
The acceleration of the truck rolling down the hill is 2 m/s² , and the force acting on it, considering its mass of 7 metric tonnes, is 14,000 Newtons.