Answer:
A chain reaction will be sustained in a sub-critical mass.
Explanation:
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Answer:
v (minimum speed) = 2.90 m/sec.

Maximum value of speed will occur at lowest point of vertical circle.
Explanation:
a) What minimum speed is necessary so that there is no tension in the string at the top of the circle but the rock stays in the same circular path?
Using the force balance expression at the top of the circle,
Gravitational Force + Tension force = Centrifugal force

Given that : T = 0
R = length of string = 0.86 m
mass of the spinning rock = 0.75 kg


v (minimum speed) = 2.90 m/sec.
b) what is the maximum speed the rock can have so that the string does not break?
Here the force balance at bottom of circle is represented by the illustration:

Given that:
maximum tension T = 45 N
maximum speed v = ??
mass m = 0.75 kg
∴

c)
At what point in the vertical circle does this maximum value occur?
Maximum value of speed will occur at lowest point of vertical circle.
This is so because at the lowest point; the tension in string will be maximum.
milligrams
Explanation:
The best unit to measure the mass of a grain of salt is the milligram.
This is about; a thousandth of a gram.
A grain of salt is a very small particle size that can still be visible with the eye.
It has a very low and small mass.
For substances like this, we use the milligram:
1000milligram = 1g
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Helping verbs come before the main verb, the main verb in the sentence is repair therefor the helping verb would be could.
I am not so sure about this it is too difficult