
Since the diameter of helium atom is approximately  , therefore the diameter of helium atom in nano meter,
, therefore the diameter of helium atom in nano meter,

 
        
             
        
        
        
Answer:
A) μ = A.m² 
B) z = 0.46m 
Explanation:
A) Magnetic dipole moment of a coil is given by; μ = NIA
Where;
N is number of turns of coil 
I is current in wire
A is area
We are given
N = 300 turns; I = 4A ; d =5cm = 0.05m
Area = πd²/4 = π(0.05)²/4 = 0.001963
So, 
μ = 300 x 4 x 0.001963 = 2.36 A.m².
B) The magnetic field at a distance z along the coils perpendicular central axis is parallel to the axis and is given by;
B = (μ_o•μ)/(2π•z³)
Let's make z the subject ;
z = [(μ_o•μ)/(2π•B)] ^(⅓)
Where u_o is vacuum permiability with a value of 4π x 10^(-7) H
Also, B = 5 mT = 5 x 10^(-6) T
Thus,
z = [ (4π x 10^(-7)•2.36)/(2π•5 x 10^(-6))]^(⅓)
Solving this gives; z = 0.46m = 
 
        
             
        
        
        
21.75 Miles Per Hour
I got this by multiplying 7.25(3) because I know 20 minutes is 1/3 of 1 he
        
             
        
        
        
Answer:
The angular  velocity is 
Explanation:
From the question we are told that 
      The mass of each astronauts is  
       The initial  distance between the two  astronauts  
Generally the radius is mathematically represented as 
       The initial  angular velocity is  
        The  distance between the two astronauts after the rope is pulled is 
Generally the radius is mathematically represented as 
 Generally from the law of angular momentum conservation we have that 
            
Here  is the initial moment of inertia of the first astronauts which is equal to
 is the initial moment of inertia of the first astronauts which is equal to  the initial moment of inertia of the second astronauts  So
 the initial moment of inertia of the second astronauts  So
       
Also    is the initial angular velocity of the first astronauts which is equal to
 is the initial angular velocity of the first astronauts which is equal to  the initial angular velocity of the second astronauts  So
 the initial angular velocity of the second astronauts  So
       
Here  is the final moment of inertia of the first astronauts which is equal to
 is the final moment of inertia of the first astronauts which is equal to  the final moment of inertia of the second astronauts  So
 the final moment of inertia of the second astronauts  So
       
Also    is the final angular velocity of the first astronauts which is equal to
 is the final angular velocity of the first astronauts which is equal to  the  final angular velocity of the second astronauts  So
 the  final angular velocity of the second astronauts  So
       
So 
       
=>   
=>   
=>    
=>   
        
 
        
             
        
        
        
C the third one i think good luck