Answer:
1. F = 45,458.17 N
2. P = 12,800,000 W
Explanation:
Part 1. The thrust force is the sum of the forces on the air and on the fuel.
For the air, 107 kg of air is accelerated from 281 m/s to 679 m/s in 1 second.
F = ma
F = (107 kg) (679 m/s − 281 m/s) / (1 s)
F = 42,586 N
For the fuel, 4.23 kg of fuel is accelerated from 0 m/s to 679 m/s in 1 second.
F = ma
F = (4.23 kg) (679 m/s − 0 m/s) / (1 s)
F = 2,872.17 N
So the thrust on the jet is:
F = 42,586 N + 2,872.17 N
F = 45,458.17 N
Rounded to three significant figures, the force is 45,500 N.
Part 2. Power = work / time, and work = force × distance, so:
Power = force × distance / time
Power = force × velocity
P = (45,458.17 N) (281 m/s)
P = 12,773,745.77 W
Rounded to three significant figures, the power is 12,800,000 W.
Answer:
The answer to this is
6600 Hz to 19,800 Hz
Explanation:
The shape of the human ear is analogous to a closed ended pipe hence
we have λ = 4L or wavelength = 4 * length of the child ear
The frequency c/λ where c = speed of sound = 343 m/s
hence the child's audible range is multiples of 343/(4*0.13) =6600Hz
or 13200 Hz or 19,800 Hz
The generally quoted range of human hearing is 20 Hz to 20 kHz
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