What's my average velocity?

Classical Mechanics Level 2

A body covers half the distance with a speed of 20 m/s and the other half with 30 m/s . What is the average speed of the body for the whole journey?


The answer is 24.

Tejashv Chaturvedi by Tejashv chaturvedi , 23, India

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6 solutions

Koringa Jayesh
Mar 16, 2014

average speed=total dist./total time. total dist.=X. for first x/2 distance time=x/40 (.'. T=D/S) and second time =x/60. so than avg. speed = X/(x/40+x/60).ans.=24 m/s

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The best way to do is to use the formula 2xy/x+y.

Anuj Shikarkhane - 6 years, 11 months ago
Bijesh Longjam
Apr 28, 2014

The time taken to cover the halves is not the same. So the average speed is just not (v1+v2)/2. It will be (total length)/total time). So x/(x/24)= 24. The answer is 24

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Sarjith Sanju
Apr 22, 2014

total distance =x, total time=x/2 (1/20+1/30), average speed= x/(x/2 (1/20+1/30))=24m/s.

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Kancherla Isaac
Mar 27, 2014

average speed=total dist./total time

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Debi Prasad Panda
Mar 15, 2014

let the totaal distance be 60 kms. half distance=30 kms. therefore @ 20 km/hr it will take 1.5 hrs to cover the distance and @ 30 km/hr it will take 1 hr. so, avg.speed=60/2.5=24 km/hr

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Robert Fritz
Mar 11, 2014

.5/20+.5/30=2.5/60=24. Add their rates doing half the distance.

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