Answer:

Explanation:
It is given that,
Frequency for submarine communications, f = 76 Hz
We need to find the wavelength of those extremely low-frequency waves. the relation between the wavelength and the frequency is given by :





or

So, the wavelength of those extremely low-frequency waves is 4000 km. Hence, this is the required solution.
Answer:
d)
Explanation:
Newton's 3rd Law tells us that for every action we will have a reaction equal in magnitude and opposite in direction. In a collision between obects A and B this means that the force on A applied by B will be equal in magnitude than the force on B applied by A, which leaves d as the true answer and the rest as false.
Because heat keeps us warm and water hydrates the planet i guess?????
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m = mass of the person = 82 kg
g = acceleration due to gravity acting on the person = 9.8 m/s²
F = normal force by the surface on the person
f = kinetic frictional force acting on the person by the surface
μ = Coefficient of kinetic friction = 0.45
The normal force by the surface in upward direction balances the weight of the person in down direction , hence
F = mg eq-1
kinetic frictional force on the person acting is given as
f = μ F
using eq-1
f = μ mg
inserting the values
f = (0.45) (82) (9.8)
f = 361.6 N