A car travels at 54 km/h for the first 20 s, 36 km/h for the next 30 s and finally 18 km/h for the next
10 s. Find its average speed.
Answers
Answer: 10.8m/s
Explanation:
54km/h=15m/s.....(1)
36km/h=10m/s.....(2)
18km/h=5m/s.......(3)
(1)speed=s/t
15=s/20
s=300m
(2)speed=s/t
10=s/30
s=300m
(3)speed=s/t
5=s/10
s=50m
average speed =total s/total t
average speed =(300+300+50)/(20+30+10)
average speed=650/60=10.8m/s
average speed =10.8m/s
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!