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:
The actual angle is 30°
Explanation:
<h2>Equation of projectile:</h2><h2>y axis:</h2>

the velocity is Zero when the projectile reach in the maximum altitude:

When the time is vo/g the projectile are in the middle of the range.
<h2>x axis:</h2>

R=Range


**sin(2A)=2sin(A)cos(A)
<h2>The maximum range occurs when A=45°
(because sin(90°)=1)</h2><h2>The actual range R'=(2/√3)R:</h2>
Let B the actual angle of projectile

2B=60°
B=30°
In rivers that are close to sea
Answer:
E = 24000 N/C = 24 KN/C
Explanation:
The electric field experienced by a test charge is given by the following formula:

where,
E = Electric Field = ?
F = Force of attraction = 3 x 10⁻⁶ N
q = Charge on piece of lint = 1.25 x 10⁻¹⁰ C
Therefore, using these values in the equation, we get:

<u>E = 24000 N/C = 24 KN/C</u>