An object covers half the distance with a speed of 20m/s and the other half with a speed of 30m/s. Calculate the average speed of the whole journey.

Asked by manhas | 13th Jun, 2016, 07:06: PM

Expert Answer:

Let the total distance traveled by the object be 's'.
Give that it covers a half the distance, i.e. (s/2) with speed 20 m/s.
begin mathsize 12px style We space know space that space rightwards arrow Speed space equals Distance over Time
Or space Time equals Distance over Speed end style 
Time taken to cover this (s/2) distance is = begin mathsize 12px style fraction numerator begin display style bevelled straight s over 2 end style over denominator 20 end fraction end style = S/40

Then it covers the other half distance, i.e. (s/2) with speed 30 m/s.
Time taken to cover this (s/2) distance is = begin mathsize 12px style fraction numerator begin display style bevelled straight s over 2 end style over denominator 30 end fraction end style = S/60
begin mathsize 12px style Average space speed space equals space fraction numerator Total space distance over denominator Total space time end fraction equals fraction numerator open parentheses straight s divided by 2 close parentheses space plus open parentheses straight s divided by 2 close parentheses over denominator open parentheses straight s divided by 40 close parentheses space plus open parentheses straight s divided by 60 close parentheses end fraction equals space 24 space straight m divided by straight s end style

Answered by Yashvanti Jain | 14th Jun, 2016, 10:28: AM

Queries asked on Sunday & after 7pm from Monday to Saturday will be answered after 12pm the next working day.