The tension in the string B) It quadruples.
Explanation:
The ball is in uniform circular motion in a horizontal circle, so the tension in the string is providing the centripetal force that keeps the ball in circular motion. So we can write:

where:
T is the tension in the string
m is the mass of the ball
v is the speed of the ball
r is the radius of the circle (the lenght of the string)
In this problem, we are told that the speed of the ball is doubled, so
v' = 2v
Substituting into the previous equation, we find the new tension in the string:

Therefore, the tension in the string will quadruple.
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They'll vibrate at their characteristic resonant frequency. That depends on the material the object is made of and its shape.
C or "Density" The granite rock has a much higher density than the Styrofoam.
Answer:
1
The mass of the Potassium-40 is 
2
The Dose per year in Sieverts is 
Explanation:
From the question we are told that
The isotopes of potassium in the body are Potassium-39, Potassium-40, and Potassium-
41
Their abundance is 93.26%, 0.012% and 6.728%
The mass of potassium contained in human body is
per kg of the body
The mass of the first body is 
Now the mass of potassium in this body is mathematically evaluated as

substituting value


The amount of Potassium-40 present is mathematically evaluated as
0.012% * 0.024


The dose of energy absorbed per year is mathematically represented as

Where E is the energy absorbed which is given as 
Substituting value


The Dose in Sieverts is evaluated as



The force of friction is 78.4 N
What is force of friction?
Frictional force is the force created when two surfaces come into contact and slide against each other. it is given by the equation:
μ * 
where,
= force of friction
μ = coefficient of friction
= normal force
Given,
μ 
We know,


Subsituing the values in equation:
μ * 

The force of friction is 78.4 N.
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