Answer:
151.9 N
Explanation:
Force = mass x acceleration
Acceleration due to gravity is 9.8 m/s^2 (you should memorize this number).
F = ma
F = (15.5)(9.8)
F = 151.9
Sound level at distance of 15 m is given as 20 dB
so intensity at this distance is given as
now if we move closer to some some distance the sound level is now 50 dB
now the intensity is given as
now we know that
so now the distance from friend must be 47 cm
<span>If the swimmer is swimming perpendicular to the current, it will take her 66m / 0.42 m/s = 157.14 seconds to cross the river. At the same time, the current will be taking her downstream at a rate of 0.32 m/s. So, when she reaches the opposite bank, her total downstream distance traveled will have been 0.32*157.14 = 50.28 meters.</span>
This interaction is known as <em>constructive interference</em>. It's a result of linear superposition.
