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

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Solution

Displacement $= 1500 m + 200 m + 2000 m = 3700 m$

Work done = Force $\times$ displacement
$= 5 N \times 3700 m = 18500 J$

Note: We do not need to calculate the circumference because we need to take displacement and not distance because displacement is change of position not distance covered by the object.

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Similar questions

Q. A boy is moving on a straight road against a frictional force of

5 N

. After travelling a distance of

1.5 k m

, he forgets the correct path at a round about (see fig.) of radius

100 m

. However, he moves on the circular path for one and half cycle and then he moves forward upto

2.0 k m

. Calculate the work done by him

(π = 3.14)

Question 12
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 of radius 100 m. However, he moves on the circular path for one and a half cycle and then he moves forward up to 2.0 km. Calculate the work done by him.

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Q. A boy is pulling a car by supplying a constant force of 8N on a straight path of 20m. On a round about of 10m diameter he forgets the path and takes 1.5 turns and then Continues on the straight path for another 20m. Find the net work done by the boy on cart

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Displacement =1500 m+200 m+2000 m=3700 mWork done = Force × displacement =5 N×3700 m=18500 JNote: We do not need to calculate the circumference because we need to take displacement and not distance because displacement is change of position not distance covered by the object.