Helium atom,  in other words, it consistis of a particle having four protons and two neutrons.
        
                    
             
        
        
        
The magnetic field generated by a wire carrying a current I is:

where r is the distance at which the magnetic field is measured, and 

 is the magnetic permeability in vacuum.
The problem says that the magnetic field at a distance r=12 cm=0.12 m from the wire must be no larger than 

. Substituting these values, we can find the maximum value of the current I that the wire can carry:
 
 
        
        
        
Answer:
0.0768 revolutions per day 
Explanation:
R = Radius
 = Angular velocity
 = Angular velocity
As the mass is conserved the angular momentum is conserved

Moment of intertia for solid sphere

Moment of intertia for hollow sphere

Dividing the moment of inertia

From the first equation

The angular velocity, in revolutions per day, of the expanding supernova shell is 0.0768 revolutions per day 
 
        
             
        
        
        
Answer:
Explanation:
given that
Distance above the ground, s = 1.2 m
Time taken by the ball, t = 3 s
Velocity of the ball, v = 1.2/3 = 0.4 m/s
Maximum height reached by the ball is then given by the formula 
H = v² / 2g
H = 0.4² / 2 * 9.8
H = 0.16 / 19.6 
H = 0.0082 m or rather, 0.82 cm