A car travels at 54 km/h for first 20 s, 36 km/h for next 30 s and finally 18 km/h for next 10 s. Find its average speed
Answers
Answer:
54 km/hr = 54 x 5/18 = 15 m/s
36 km/hr = 36 x 5/18 = 10 m/s
18 km/hr = 18 x 5/18 = 5 m/s
1st Case ---
Speed = 15m/s
Time = 20 s
Distance = Speed x Time = 15 x 20 = 300 m
2nd Case ---
Speed = 10 m/s
Time = 30 sec
Distance = 10 x 30 = 300 m
3rd Case ---
Speed = 5 m/s
Time = 10s
Distance = 5 x 10 = 50 m
Now Total Distance = 300 + 300 + 50 = 650 m
Total time = 20 + 30 + 10 = 60 s
Average Speed = 650/60 = 65/6 m/s
Explanation:
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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!