<h2>
Answer: Marie Curie's notebooks</h2>
Explanation:
Marie Curie's notebooks, as well as all of her belongings, including her clothes, were contaminated with ionizing radiation. In fact, also those of her husband, because <u>this couple of scientists discovered the radioactivity of several elements</u>, helping the advance of science, but did not know about the consequences of dealing with these materials without adequate protection.
It should be noted that Curie's notes are stored in the basements of the National Library of France, stored in thick lead boxes and those who wish to access these documents must follow the appropriate protocol to treat radioactive material, wear appropriate clothing and sign a responsibility agreement before allowing them to review the documents.
Answer:
a) 
b)
Explanation:
Let´s use Doppler effect, in order to calculate the observed frequency by the byciclist. The Doppler effect equation for a general case is given by:
where:
Now let's consider the next cases:
The data provided by the problem is:
The problem don't give us aditional information about the medium, so let's assume the medium is the air, so the speed of sound in air is:
Now, in the first case the observer alone is in motion towards to the source, hence:
Finally, in the second case the observer alone is in motion away from the source, so:
Answer:
0.52 m
Explanation:
The motion of the studnet is an accelerated motion, with constant acceleration 
(acceleration of gravity) toward the ground. We can find the distance covered by the student (which is equal to the height from which he falls) by using the SUVAT equation:
where
v = 3.2 m/s is the final speed
u = 0 is the initial speed
a = 9.8 m/s^2 is the acceleration
d is the distance covered
By re-arranging the equation, we find:
Answer:
Distance = 16.9 m
Explanation:
We are given;
Power; P = 70 W
Intensity; I = 0.0195 W/m²
Now, for a spherical sound wave, the intensity in the radial direction is expressed as a function of distance r from the center of the sphere and is given by the expression;
I = Power/Unit area = P/(4πr²)
where;
P is the sound power
r is the distance.
Thus;
Making r the subject, we have;
r² = P/4πI
r = √(P/4πI)
r = √(70/(4π*0.0195))
r = √285.6627
r = 16.9 m
