I only know about the Water tank which is the most accurate. You place your body in it, and weights are added I think. Somehow some measurements are gathered to get your body fat weight. Online calculators exist, as well as electronic waves that are sent int your body, the echo is recorded and analyzed.
Answer:
b) 472HZ, 408HZ
Explanation:
To find the frequencies perceived when the bus approaches and the train departs, you use the Doppler's effect formula for both cases:

fo: frequency of the source = 440Hz
vs: speed of sound = 343m/s
vo: speed of the observer = 0m/s (at rest)
v: sped of the train
f: frequency perceived when the train leaves us.
f': frequency when the train is getTing closer.
Thus, by doing f and f' the subjects of the formulas and replacing the values of v, vo, vs and fo you obtain:

hence, the frequencies for before and after tha train has past are
b) 472HZ, 408HZ
Velocity 0.86m/s
0.13J
Explanation:
Given parameters:
Mass = 0.343kg
distance = 5m
time taken = 5.8s
Unknown:
Velocity of mass = ?
Kinetic energy = ?
Solution:
Velocity is the rate of change of displacement with time. It is a vector quantity that shows magnitude and direction.
Mathematically;
Velocity =
Velocity =
= 0.86m/s
Kinetic energy is the energy due to the motion of a body. It is expressed mathematically as:
Kinetic energy = 
m is the mass
v is the velocity
Kinetic energy =
= 0.13J
learn more:
Kinetic energy brainly.com/question/6536722
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