To minimize neutron leakage from a reactor, the ratio of the surface area to the volume should be a minimum. For a given volume V the ratio of the sphere will be
.
We know that the surface area and volume of the sphere is given by:

Therefore, the ratio between the surface area and the volume for the sphere will be:

Equating the volume to the constant c, we will find the value of
.

Substituting the value of r in the ration between surface area and volume, we get:

Calculating the constants, we get:

Hence, the ration between surface area and volume is 
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Answer:
3 m/s
Explanation:
Average Speed = 
Plug in the numbers, it will be (6m + 3m) divided by (2s + 1s), which is 9m/3s, which equals to 3m/s.
6x2=12m
6x18=108
12m+108
Simplified: m+9 bc 12/12 and 108/12
Answer:
8 m west
Explanation:
If we say east is the +x direction, and west is the -x direction, then the displacement is:
Δx = 12 m + (-20 m)
Δx = -8 m
Answer:
Position =
behind the mirror
Nature = Virtual and Erect
Size =
: Diminished
Explanation:
Sign convention-Distance measured to the left of pole is negative and to the right of pole is positive.
Object distance = u = -20 cm
Focal length = f = Radius of curvature/2 = 30/2 = 15 cm
We have to use mirror formula to find image distance.

Since the image distance is positive, it is formed behind the mirror or a virtual image is formed.
Magnification = 

Height of the object = 5 cm
Height of the image = 
Since the height of the image is positive and less than the size of object,it is erect and diminished.