The half-life observed by an observer at rest is 1.25 s
Explanation:
In this problem, the particle is travelling at a significant fraction of the speed of light: therefore, we have to consider the phenomenon of the time dilation. The half-life of the particle as measured by an observer at rest is given by
where
is the proper half-life of the particle
v is the speed of the particle
c is the speed of light
For the particle in this problem,
Substituting into the equation, we find:
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<h2>
Answer: an underground lake</h2>
Explanation:
In general, sound (mechanical waves) travels faster in solids than in liquids, and faster in liquids than in gases. This is because <u>the speed of the mechanical waves is determined by a relationship between the elastic properties of the medium </u>in which they are propagated and the mass per unit volume of the medium (that is:<u>density</u>).
In other words: The speed of sound varies depending on the medium through which the sound waves travel.
So, if we are told the sound wave initially had a speed of 4,000 m/s and it suddenly decreases to 1,500 m/s, this means the sound waves passed from a solid medium to a liquid medium.
Hence, the correct option is: an underground lake.
(a) Intensity obeys inverse square law from basis of light passing through a given surface.
(b) Gravitation obeys inverse square law from the basis of force between two masses.
(c) The maximum magnitude of the acceleration of the block is 126.75 m/s².
<h3>
What is intensity?</h3>
Intensity is the ratio is ratio of power to area of a given surface.
I = P/A (W/m²)
where;
<h3>Universal gravitation law</h3>
Intensity and gravitation do not obey inverse square law for same reason;
- Intensity obeys inverse square law from basis of light passing through a given surface.
- Gravitation obeys inverse square law from the basis of force between two masses.
<h3>Acceleration of the block</h3>
a = v²/A
a = (3.9²)/0.12
a = 126.75 m/s²
Learn more about acceleration here: brainly.com/question/605631
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