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 tonnes  (Hint: 1 tonne = 1000 kg.)

Initial velocity of the truck, u=0 m/s

Distance covered by the truck, S=400 m

Time taken to cover that distance, t=20 s

Let the acceleration of the truck be  'a'

S= u t + (1/2) a t²

400=(0)20+ (1/2) ​a (20)²  

The acceleration of the truck a=2 m/s²

Mass of the truck    m =7 tonnes = 7000 kg        (∵1 tonne=1000 kg)

F = m a =7000×2 =14000 N    

The force acting on truck is 14000 N.