Question

A body travels a distance of 10 km with a constant
speed of 30 km h l and then the next 40 km at a
constant speed of 50 km h . Find the average speed
for the whole journey.​

Answer 1

this is the anwer,

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Answer 2

Let distance d1=10km

and distance d2=40km.

a=0(Since speed is constant).

=>u1=v1=30km/hr

and u2=v2=50km/hr.

time taken for d1 be t1 and time taken for d2 be t2.

Since d=ut+1/2at²

=>d1=ut1+1/2at1²

=>10=30t1+0(since a=0)

=>t1=1/3s

Similarly, d2=u2t2+1/2at2²

=>40=50t2+0

=>t2=4/5

=>t2=0.8s

=>Average Speed for the whole journey=d1+d2/t1+t2

=>Avg Speed=10+40/1/3+4/5

=>Avg Speed=50/17/15

=>Avg Speed =50×15/17

=>Avg Speed=750/17km/hr

Hope it is helpful.