Question

A body travels with a speed of 5 ms for 12 seconds with speed 18 m s for the next one second. The average speed for the whole journey is (1) 5 ms-¹

(2) 6 ms-¹

(4) 8 ms -1

(3) 7ms. with explanation​

Answer 1

for initial 12 second,

t'=12 second

v'=5m/s

distance (s')= t'×v'=12×5=60m

for last one second,

t=1 second

v=18m/s

distance (s)=v×t=18×1=18m/s

now,total distance(d)=60+18=78m

total time(T)=12+1 second=13 second

average speed=total distance/total time

so, avg. speed=78/13=6 m/s