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.
Answer:
The statement that best describes insulators is <u><em>"Electrons within their atoms are strongly held by the nuclei"</em></u>
Explanation:
Atoms are constituted by a nucleus with positive charge (protons and neutrons), around which negative charges (electrons) revolve.
Substances that have a huge amount of "free electrons" that can move through the material are called conductors. This is due to the low resistance to the movement of the load or electric current.
Materials that do not conduct electricity are called insulators. In this case the electrons are strongly bound to the nucleus and cannot move freely. In this way a great resistance to the flow of electric current is offered.
Finally, semiconductors are the materials that can have electrical properties of conductors or insulators.
So<u><em> the statement that best describes insulators is "Electrons within their atoms are strongly held by the nuclei"</em></u>
Answer:
When two tectonic plates meet, we get a “plate boundary.” There are three major types of plate boundaries, each associated with the formation of a variety of geologic features.
Explanation:
Answer:
Explanation:
If an object has a higher density than the fluid it is in (fluid can mean liquid or gas), it will sink. If it has a lower density, it will float. Density is determined by an object's mass and volume. If two objects take up the same volume, but have one has more mass, then it also has a higher density.