Answer:at 21.6 min they were separated by 12 km
Explanation:
We can consider the next diagram
B2------15km/h------->Dock
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B1 at 20km/h
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V
So by the time B1 leaves, being B2 traveling at constant 15km/h and getting to the dock one hour later means it was at 15km from the dock, the other boat, B1 is at a distance at a given time, considering constant speed of 20km/h*t going south, where t is in hours, meanwhile from the dock the B2 is at a distance of (15km-15km/h*t), t=0, when it is 8pm.
Then we have a right triangle and the distance from boat B1 to boat B2, can be measured as the square root of (15-15*t)^2 +(20*t)^2. We are looking for a minimum, then we have to find the derivative with respect to t. This is 5*(25*t-9)/(sqrt(25*t^2-18*t+9)), this derivative is zero at t=9/25=0,36 h = 21.6 min, now to be sure it is a minimum we apply the second derivative criteria that states that if the second derivative at the given critical point is positive it means here we have a minimum, and by calculating the second derivative we find it is 720/(25 t^2 - 18 t + 9)^(3/2) that is positive at t=9/25, then we have our answer. And besides replacing the value of t we get the distance is 12 km.
The official web site of the Nobel Prize explains that Marie Curie’s chemistry prize was partly for her discovery that the radioactivity of a substance is unaffected when it undergoes a chemical reaction. The discovery implied was that, Radioactivity involves Radioactivity involves only neutrons.
Explanation:
- The official web site of the Nobel Prize explains that Marie Curie’s chemistry prize was partly for her discovery that the radioactivity of a substance is unaffected when it undergoes a chemical reaction. The discovery implied was that, Radioactivity involves only neutrons.
- Marie Curie studied about the radiation of all compounds containing the known radioactive elements, including uranium and thorium, which she later discovered that they were radioactive.
- she discovered the following results,
- the exact measurement of the strength of the radiation from uranium;
- the intensity of the radiation was found to be proportional to the amount of uranium or thorium in the compound .
- the ability to emit radiation is not dependent on the arrangement of the atoms in a molecule;
- it must be linked to the interior of the atom itself which is a revolutionary discovery.
From the calculation, the gravitational force of attraction is 1.33 * 10^-14 N.
<h3>What is the gravitational force?</h3>
The gravitational force is an attractive force that acts between any two masses.
It is given by;
F = Gm1m2/r^2
F = 6.67 * × 10−11 * 2.5 * 5/(250)^2
F = 83.4 × 10−11 /62500
F= 1.33 * 10^-14 N
Learn more about gravitational force:brainly.com/question/12528243
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Answer:
A the type of dog food because it was different and every other thing was the same.