A car travels at 54 km/hr for first 20 seconds, 36 km/hr for next 30 seconds and finally 18 km/hr for next 10 seconds. Find its average speed.
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Answered by
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The speed of car @ 30 km/h= 75/9 m/s
The speed of car@ 40 km/h= 100/9 m/s
The speed of car @ 50 km/h= 125 m/s
Distance covered by the car in 1 s @ 30 km per hour, in two seconds @ 40 km per hour and in 3 seconds @ 50 km per hours = (75/9)(1)+(100/9)(2)+(125/9)(3)=(650/9) metre in 6 seconds.
Average speed= (650/9)÷6= 650/54 metre per second=(130/3) km/h= 43.33 km/h.
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Answered by
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Hey there!
Formula used:
• Distance = speed * time
• Speed ( in 1 km/h) = 5 /18 (in 1 m/s)
Distance covered when car travels at 54 km/h for first 20 s:
Speed = 54 km / h
= 54 *( 5/18) m/s
= 15 m/s
Distance (d₁) = speed * time
= 15 * 20 = 300 m
Distance covered when car travels at 36 km/h for 30 s:
S = 36 km/h = 36 * (5/18) m / s = 10 m/s
d₂ = v * t = 10 * 30 = 300 m
Distance covered when car travels at 18 km/h for 10 s:
S = 18 km/h = 18*(5/18) m/s = 5 m/s
d₃ = v * t = 5 * 10 = 50 m
Average speed = Total distance(d₁ + d₂ + d₃) / Total time
= (300 + 300 + 50) m / (20 + 30 + 10) s
= (650 m) / 60 s
= 10.83 m/s (←Answer)
Good day!
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