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To develop this problem it is necessary to apply the concepts related to a magnetic field in spheres.
By definition we know that the magnetic field in a sphere can be described as

Where,
a = Radius
z = Distance to the magnetic field
I = Current
Permeability constant in free space
Our values are given as
diameter of the sphere then,

Thus z = a



Re-arrange to find I,



Therefore the current at the pole of this sphere is 
Answer:
"Scientist use radioactive decay to measure the age of a rock or fossil."
Explanation:
"To establish the age of a rock or a fossil, researchers use some type of clock to determine the date it was formed. Geologists commonly use radiometric dating methods, based on the natural radioactive decay of certain elements such as potassium and carbon, as reliable clocks to date ancient events."
Explanation:
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What is the kinetic energy of the system after the collision?

How this is calculated?
Given:
Initial speed=
mass of rod=M
Let, Initial kinetic energy =
Final kinetic energy=
Moment of inertia =I
What is the moment of inertia?

What is the angular momentum?
By conservation of angular momentum,


We know that, the final kinetic energy is given by,

What is the kinetic energy?
- In physics, the kinetic energy of an object is the energy that it possesses due to its motion.
- It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity.
- Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes.
To know more about kinetic energy, refer:
brainly.com/question/114210
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