Question 38:
The distance between Delhi and Agra is 200 km. A train travels the first 100 km at a speed of 50 km/h. How fast must the train travel the next 100 km, so as to average 70 km/h for the whole journey ?
Lakhmir Singh Physics Class 9
Answers
Answered by
1
the speed that train travel next 100 km,so as to average 70 km for the whole journey is 90 km/h.
Answered by
2
Total distance = 200 km
Speed for first 100 km = 50 km/hr
let speed for next 100 km be x km/hr
Time taken for first 100 km( t1)= 100/50= 2 hrs
Time taken for next 100 km(t2)= 100/x hrs
We know that,
Average speed = total distance covered/ total time taken
therefore,
70 = 200/2+100/x
=> 70 = 200x/2x+100
=> 140x +7000= 200x
=> 7000= 60x
=> x= 116.67km/hr
Speed for first 100 km = 50 km/hr
let speed for next 100 km be x km/hr
Time taken for first 100 km( t1)= 100/50= 2 hrs
Time taken for next 100 km(t2)= 100/x hrs
We know that,
Average speed = total distance covered/ total time taken
therefore,
70 = 200/2+100/x
=> 70 = 200x/2x+100
=> 140x +7000= 200x
=> 7000= 60x
=> x= 116.67km/hr
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