Question

-1
15. A body goes from P to Q with a
velocity of 40 ms and comes
back from Q to P with a velocity of
60 ms-1. Then, the average
velocity of the body during the
whole journey is
(a) 50 ms -1
(c) 45 ms
(dt zero
(b) 48 ms -1
-1​

Answer 1

Answer:-

Let the Distance between P and Q be d.

Given:-

A body goes from P to Q with a velocity of 40 m/s.

We know that,

Time = distance/speed (or) velocity

→ Time taken by the body to travel from P to Q = (d/40) s.

And,

Time taken to return from Q to P = (d/60) s

We know that,

Average velocity = Total displacement/total Time

• Total Displacement = distance between Q & P - Distance between P & Q = d - d

• Total Time = d/40 + d/60

→ Average velocity of the body = (d - d) / [ (d/40) + (d/60) ]

→ Average velocity of the body = 0 * [ 1/ (d/40) + (d/60) ]

→ Average velocity of the body = 0 m/s.

Therefore, the Average Velocity of the body is 0 m/s.

Answer 2

Answer:

c) zero

Explanation:

Average velocity is defined as the ratio of total displacement with respect to total time taken.

Method 1)

As the body starts from point P to Q and then comes back from Q to P. Here, the initial and final velocity of the body is same. Therefore, the average velocity of the body during the whole journey is 0 m/s.

Method 2)

Time = Displacement/Speed

Displacement = x (say)

t1 = x/40 and t2 = x/60

Total displacement = x - x = 0 m

Total time = t1 + t1 = x/40 + x/60

Average velocity = Total displacement/Total time

= 0/(x/40 + x/60)

= 0

Hence, the average velocity of the body during the whole journey is 0 m/s.