Question

A boy is moving on a straight road against a

frictional force of 5 N. After travelling a distance

of 1.5 km he forgot the correct path at a round

about (Fig. 11.1) of radius 100 m. However,

he moves on the circular path for one and half

cycle and then he moves forward upto 2.0 km.

Calculate the work done by him.​

Answer 1

Given :-

Frictional force of the boy moving = 5 N

Distance travelled first = 1.5 km

Distance travelled through the correct path = Radius 100 m

Distance travelled upwards = 2 km

To Find :-

The work done by the boy.

Analysis :-

Firstly find the total distance covered by the boy by adding up all the values of distance given in the question.

Then find the work done accordingly such that work done is equal to force multiplied by the displacement.

Solution :-

We know that,

s = Displacement

f = Force

w = Work done

Values of the distance

d₁ = 1.5 km = 1500 m

d₂ = 200 m (Diameter - 2d = 2 × 100)

d₃ = 2 km = 2000 m

Total distance,

Total distance = d₁ + d₂ + d₃

= 1500 + 200 + 2000

= 3700 m

Using the formula,

$\underline{\boxed{\sf Work \ done=Force \times Displacement}}$

Given that,

Force (f) = 5 N

Displacement (s) = 3700 m

Substituting their values,

⇒ w = f × s

⇒ w = 5 × 3700

⇒ w = 18500 J

Therefore, the work done by the boy is 18500 J.