If the echo (the reflected sound) reaches your ear less than about
0.1 second after the original sound, your brain doesn't separate them,
and you're not aware of the echo even though it's there.
If the echo comes from, say, a wall, 0.1 second means you'd have to be
about 17 meters away from the wall. If you're closer than that, then the
echo reaches you in less than 0.1 second and you're not aware of it.
A. 30 meters . . .
No. You hear that echo easily
B. you're standing within range of both sounds . . .
No. You hear that echo easily, if you're at least 17 meters from the wall.
C. less than 0.1 second later . . .
That's it. The echo is there but your brain doesn't know it.
D. 21.5 meters
No. You hear that echo easily.
90 kilometers because you need to multiply 40 by 2 and then you get 80 and finally you add 10 and get 90 kilometers
Answer:
speed = 3.95 m/s
Explanation:
area = π x radius^2
area = π x (2.67 x 10^-3)^2
volume flow rate = area x speed
volume / time = area x speed
density = mass / volume
volume = mass / density
<u>mass / (density x time) = area *speed</u>
mass flow rate = mass / time
<u>mass flow rate / density = area x speed</u>
6.55 x 10^-2 / 740 = pi * (2.67 x 10^-3)^2 * speed
speed =8.8514 x 10-5 /2.2396 x 10-5 m/s
speed = 3.95 m/s
