5. 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.)
Answers
given data,
Initial velocity =u=0
Distance =s=400m
time =t=20sec
a= acceleration
We know that,
Equation of motion:-
s=ut+
2
1
at
2
400=0+
2
1
×a×20×20
400=200a
a=2
acceleration =a=2m/s
2
Force =F=?
The force acting on the mass is 7 tonnes(∴1tonne=1000Kg)
Mass m=7×1000=7000Kg
Mass =m=7000kg
Acceleration =a=2m/s
2
F=ma
=7000×2
=14000N
Explanation:
Hi...
Since the truck starts from rest, initial velocity(u) = 0 m/s
Displacement(S) = 400m, Time(t) = 20s and Acceleration(a) = ?
So...you can use the second equation of motion to find the acceleration...
S = ut + 1/2at²
Substitute the values and solve...
400 = (0)(20) + 1/2(a)(20)²
400 = 0 + 1/2(a)(400)
400 = 200(a)
Hence, Acceleration(a) = 2m/s²
Now, the formula to find force = Mass × Acceleration
= 7(1000) kg × 2 m/s²
= 14000 N...(N-->Newton)
I hope it helps...