Question

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

Answer 1

The truck starts from rest, so initial velocity = 0

Distance travelled = 400 m

Time taken = 20 s

We know the equation of motion, S = ut + ½ at2

400 = 0 + ½ a * (20)2

a = 2 m/s2

Now, mass = 7 metric tonnes

= 7 * 1000

= 7000 kg

So force = mass * acceleration

F = 7000 * 2

= 14000 N

Answer 2

Given,

Distance travelled by the truck=400m

Time taken =20s

Mass=7 metric tonnes

To Find,

Force acting on it.

Solution,

The truck starts from rest.

so its initial velocity ,u = 0

Distance travelled by it= 400 m

Time taken to cover the distance = 20 s

We have the equation of motion,

S = u× t + 1/2at²

⇒400 = 0 +1/2× a ×(20)²

⇒400=1/2×a×400

⇒400=200a

⇒a=2m/s²

Now, it is given that mass = 7 metric tonnes

To convert it into kg = 7 × 1000

                                   = 7000 kg

So force = mass ×acceleration

           F = 7000 ×2

             = 14000 N

Hence, force acting on it is 14000N.