Question

A boy is moving on a straight road against a frictional force of $5N$. After travelling a distance of $1.5km$, he forgets the correct path at a round about (see fig.) of radius $100m$. However, he moves on the circular path for one and half cycle and then he moves forward upto $2.0km$. Calculate the work done by him $(\pi =3.14)$

Answer 1

Total distance travelled by the boy = 1500 m + 200 m + (1.5 x 2 πr)

Total distance travelled by the boy = 1500 m + 200 m + (1.5 x 2 x 3.14 x 100)

Total distance travelled by the boy = 4442 m

Because frictional force is a non-conservative force so the total distance travelled should be considered as the total displacement to calculate the work done against the frictional force.

Frictional force = 5 N

Workdone = Force × Displacement

W = F × D

Workdone (W) = 5 × 4442

W = 22210 J.