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:
Explanation:
Given that,
The mass of a Hubble Space Telescope, 
It orbits the Earth at an altitude of 
We need to find the potential energy the telescope at this location. The formula for potential energy is given by :
Where
is the mass of Earth
Put all the values,
So, the potential energy of the telescope is 
.
I would use miles
Because miles will give you less of an answer
Answer: Hello!
Lewis is travelling at 165 mph, which means miles per hour, this says that he does 165 miles in one hour.
We want to know how much time takes to cover 16 miles.
this can be calculated as the quotient of the distance and the velocity; this is:
if we want to write this in minutes, then:
we know that one hour has 60 minutes, then 0.096 hours has:
0.096h*60mins/1h = 5.8 minutes.
then Lewis needs 5.8 minutes in order to cover 16 miles if his speed is 156 miles per hour.
