Question

A body travel from a point P to a point Q by the shortest route with a velocity of 50 km/h
and returns to P by the same route with a velocity of 70 km/h What is its average speed?
Ans: 58.33 km/hr)​

Answer 1

Explanation:

since speed = distance/time (since it's the shortest path the distance and speed are equal to displacement and velocity respectively)

let distance between p and q be PQ

therefore 50=PQ/t1...(1)

70=PQ/t2...(2)

t1+t2=PQ/50+PQ/70

total time= (70PQ+50PQ)/3500

T=120PQ/3500

T=12PQ/350

since average velocity is total distance/total time

since total distance is 2PQ since it returned back.

average v=2PQ÷(12PQ/350

=2PQ×350/12PQ

=2×350/12

=350/6

=58.33 km/hrs.