Question

boy starts from a point A, travels to a point B at a distance of 3 km from A and returns to A. If he takes two hours to do so, his speed is
1 point
3 km/h
zero
2 km/h
1.5 km/h
​

Answer 1

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Given info : A body starts from a point A, travels to a point B at a distance of 3 km form A returns to A.

=>To find : if he takes two hours to do so, his speed is ...

=>solution : speed of a body is the rate of change of distance covered by the body with respect to time.

=>i.e., speed = total distance covered/total time taken

=>here total distance covered by the boy = distance between A and B + distance B and A = 3 km + 3 km = 6 km

=>total time taken by the boy = 2 hrs

=>now the speed of the boy = 6 km/2 hrs = 3 km/h

:-Therefore the speed of the boy is 3 km/h.

[note : here total displacement of the boy will be zero because initial position and final position of boy are same. so the average velocity of the boy will be zero. ]

Answer 2

Given:

A boy starts from a point A, travels to a point B at a distance of 3 km from A and returns to A. Time taken is 2 hours.

To find:

Average speed of boy?

Calculation:

• Average it can be calculated by dividing the total distance with the total time.

• Let average speed be 'v'.

$\therefore \: v = \dfrac{total \: distance}{total \: time}$

$\implies \: v = \dfrac{3 + 3}{2}$

$\implies \: v = \dfrac{6}{2}$

$\implies \: v = 3 \: km/hr$

So, average speed of boy is 3 km/hr.

• Please note that average velocity will be ZERO in this case because the displacement is ZERO.