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7. A motor cyclist goes from station A to B at 40 km h ' andthen returns from B to A at 120 kmh-. Calculate (i) averagespeed (ii) average velocity during the round trip.[Ans. (i) 60 km h-(ii) zero]3 |
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Answer» Acc. To me, Answer is a) 60 km/h b) 0 --------------------------------------------- A) s1(SPEED of going)=40km/h s2(speed of returning)=120km/h d=x km ---------------------------------------------------- Here i derive formula if you don't want DERIVATION then USE formula that is in eq 3 Avg speed =total distance/total time Total d=d+d(for going and returning) and d is same total time=t1+t2(for going and returning) You don't KNOW time so find out by s=d/t For t1(going) s=s1,d=d,t=t1 so t1=d/s1---------1 Here for t2(returning) s=s2,d=d,t=t2 t2=d/s2------------2 Put it and find avg S=2d/t1+t2 avg S=2*s1*s2/s1+s2------3 ----------------------------------------------------------------- Put s1 and s2 in equation 3 and find Avg S=60 km/h B) Average velecity =Total displacement /total time Here cyclist GO an return to same place so displacement is zero If you put displacement =0 then velocity =0 |
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