A light aircraft flies in a semi-circle from point A to point B. If the circle has a radius of 20km and the time taken is 30 minutes, the average speed is
- 125.7 km/h.
- 251.4 km/h.
- 62.83 km/h.
Explanation
Average speed is path length divided by time. A semicircle of radius 20 km has an arc length of pi x 20 = 62.83 km, covered in 0.5 hour, giving 62.83 / 0.5 = 125.7 km/h. The distractor 251.4 results from doubling, and 62.83 confuses speed with the raw distance figure.
giovanni asking:
how?? thanks
Community Comments (3)
S
samed1997 Posts: 4 29.04.2017 / 16:44
circumference= 2piR
circumference semicircle= piR
V=S/t= (20pi)/0.5= 40pi Km/h = 125 Km/h
circumference semicircle= piR
V=S/t= (20pi)/0.5= 40pi Km/h = 125 Km/h
G
giovanni Posts: 2 29.04.2017 / 16:46
thank you!
J
Jordi Posts: 198 14.06.2020 / 15:49
the formula is V=2πr/T
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