Question

A man travel half length of a straight road with a constant speed of 20 m/sec. and he travel the second half length of the road with a constant speed 60m/sec. then calculate its average speed

Answer 1

Answer:

Explanation:

Answer was

2v1.v2/v1+v2

2.20.60/80

30m/s was answer

Answer 2

Answer:

30 m/sec

Explanation:

Let's consider that the total length of the road is x. Then according to question, it is given that

Man travels half distance with a speed,V1=20m/s

hence,time taken to travel first half distance, t1= distance/speed

= x/2*v1

= x/2*20

= x/40 sec

Man travels another half distance with a speed,V2=60m/s

hence time taken to travel other half distance,t2=distance/speed

= x/2*v2

=x/2*60

= x/120sec

total time taken by a man to cover the whole distance, t= t1+t2

= x/40+x/120

= x/30

So, the average speed can be given by

V= total distance travelled/ total time taken

=x/x/30

=30m/sec

hence the average speed of the man is 30m/sec