Second moment of area about an axis along any diameter in the plane of the cross section (i.e. x-x, y-y) is each equal to (1/4)pi r^4.
The second moment of area about the zz-axis (along the axis of the cylinder) is the sum of the two, namely (1/2)pi r^4.
The derivation is by integration of the following:
int int y^2 dA
over the area of the cross section, and can be found in any book on mechanics of materials.
5.25 gallons is your answer
let
r--------> Alvin's average paddling rate in km/hour
y -------> speed of the current
in km/hour
we know that
speed= distance/time
------> solve for distance
distance=speed*time
to Campsite against the current
speed=r-y-----> speed=(r-3)
time=8 hours
distance=(r-3)*8------> equation 2
From Campsite with the current
speed=r+y-----> speed=(r+3)
time=3 hours
distance=(r+3)*3------> equation 1
equate equation 1 and equation 2-----> because is the same distance
(r+3)*3=(r-3)*8----> 3r+9=8r-24----> 8r-3r=24+9-----> 5r=33----> r=6.6 km/hour
therefore
the answer is
Alvin's average paddling rate is 6.6 km/hour
Answer: When two or more lines cross each other in a plane, they are called intersecting lines. The intersecting lines share a common point, which exists on all the intersecting lines, and is called the point of intersection. Here, lines P and Q intersect at point O, which is the point of intersection.
I think this the answer♀️
