Answer:
Incomplete question 
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For a magnetic field strength of 2 T, estimate the magnitude of the maximum force on a 1-mm-long segment of a single cylindrical nerve that has a diameter of 1.5 mm. Assume that the entire nerve carries a current due to an applied voltage of 100 mV (that of a typical action potential). The resistivity of the nerve is 0.6ohms meter
Explanation:
Given the magnetic field 
B=2T
Lenght of rod is 1mm
L=1/1000=0.001m
Diameter of rod=1.5mm
d=1.5/1000=0.0015m
Radius is given as
r=d/2=0.0015/2
r=0.00075m
Area of the circle is πr²
A=π×0.00075²
A=1.77×10^-6m²
Given that the voltage applied is 100mV
V=0.1V
Given that resistive is 0.6 Ωm
We can calculate the resistance of the cylinder by using 
R= ρl/A
R=0.6×0.001/1.77×10^-6
R=339.4Ω
Then the current can be calculated, using ohms law
V=iR
i=V/R
i=0.1/339.4
i=2.95×10^-4 A
i=29.5 mA
The force in a magnetic field of a wire is given as
B=μoI/2πR
Where 
μo is a constant and its value is
μo=4π×10^-7 Tm/A
Then,
B=4π×10^-7×2.95×10^-4/(2π×0.00075)
B=8.43×10^-8 T
Then, the force is given as
F=iLB
Since B=2T
F=iL(2B)
F=2.95×10^-4×2×8.34×10^-8
F=4.97×10^-11N
 
        
             
        
        
        
Answer: 20
Explanation: Mass number is the number of neutrons plus the number of protons. 8 + 12 gives 20.
 
        
             
        
        
        
The gravitational force between two object depends on their masses and on their distance.
Since the formula is

If the masses grow, the force also grows. But I'm assuming the two objects are fixed, so you can't enlarge their mass.
So, the only option remaining is to lower their distance: since it sits at the denominator, a smaller value of d results in a bigger value for F.
So, if you reduce the distance between two objects, the gravitational force between them will always result in an increase
 
        
             
        
        
        
B. Helium because it is constantly being made in the sun
Explanation:
From the given paragraph, we can conclude that helium is the most common element in a star such as the sun because it is constantly being made. 
In the nuclear fusion process that results in the production of helium, hydrogen nuclei are the reactants and helium is the product. 
- since the reactants are constantly being used in the core of the sun, this suggests that the products must be more. 
- The reaction requires a high temperature and pressure to initiate. 
- It is a series of chain reaction that uses a fuel of hydrogen to produce helium. 
learn more: 
Transmutation brainly.com/question/3433940
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