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

U can do also like this👇👇👇 the truck starts from rest so u=0 s=ut+1/2 at'2 s=400, t =20, we should find acceleration s=ut+1/2 at''2 400=[0]20+1/2[a] [20] [20] 400=0+1/2[400] [a] 400=[200] [a] 400/200=a 2=a f=ma [1tonne]=1000kg then 7 tonne=[7] [1000] m =7000 a=2 f=ma f=[7000] [2] =14000 N

Ass it is wrong

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U= 0
S= 400m
Time taken= 20s

S=m+1/2 at2 2 is square
Acceleration=a
400=0+1/2a (20)square

400=1/2a(400)
A=2m/s square
1 metric ton=1000kg
7 metrix tons=7000kg

Mass of truck=7000kg
F=ma
F= 7000*2
=1400N

i also think it  is wrong