A body goes from P to Q with a velocity of 10 m/s and comes back from Q to P with a velocity of 20 m/s. What is the average velocity of the body during the entire trip?

zero

because the body went nowhere

To find the average velocity of the body during the entire trip, we need to calculate the total displacement and total time taken.

Let's assume that the distance from P to Q is d.

During the first part of the trip from P to Q, the velocity is 10 m/s. The time taken for this leg of the trip can be calculated as t1 = d / 10.

During the return trip from Q to P, the velocity is 20 m/s. The time taken for this leg of the trip can be calculated as t2 = d / 20.

The total displacement for the round trip is zero since the starting and ending points are the same.

The total time taken for the round trip can be calculated as the sum of the outbound and return journey times: t_total = t1 + t2.

Therefore, the average velocity can be calculated as:

Average Velocity = Total Displacement / Total Time
= 0 / t_total
= 0 m/s

Hence, the average velocity of the body during the entire trip is 0 m/s.