The answer is D. Isotopes.
Hope that helped.
        
                    
             
        
        
        
Answer:
Net force on the block is 32 N.
Acceleration of the object is 6.4 m/s².
Explanation:
Let the acceleration of the object be  m/s².
 m/s².
Given:
Mass of the block is, 
Force of pull is, 
Frictional force on the block is, 
The free body diagram of the object is shown below.
From the figure, the net force in the forward direction is given as:

Now, from Newton's second law of motion, net force is equal to the product of mass and acceleration. So,

Therefore, the acceleration of the object in the forward direction is 6.4 m/s².
 
        
             
        
        
        
Answer:
A) The north pole of a bar magnet will attract the south pole of another bar magnet. 
B) Earth's geographic north pole is actually a magnetic south pole. 
E) The south poles of two bar magnets will repel each other.
Explanation:
<u>According to </u><u>classical physics</u>, a magnetic field always has two associated magnetic poles (north and south), the same happens with magnets. This means that if we break a magnet in half, we will have two magnets, where each new magnet will have a new south pole, and a new north pole. 
This is because <u>for classical physics, naturally, magnetic monopoles can not exist. </u>
In this context,  Earth is similar to a magnetic bar with a north pole and a south pole. This means, the axis that crosses the Earth from pole to pole is like a big magnet.  
Now, by convention, on all magnets the north pole is where the magnetic lines of force leave the magnet and the south pole is where the magnetic lines of force enter the magnet.  
Then, for the case of the Earth, the north pole of the magnet is located towards the geographic south pole and the south pole of the magnet is near the geographic north pole.  
And it is for this reason, moreover, that the magnetic field lines enter the Earth through its magnetic south pole (which is the geographic north pole).
 
        
             
        
        
        
2ω is the resistance of the second wire if the resistance of the first is 4ω if two wires have the same length, but the second has twice the diameter of the first.
R= 4ω.
R = ρl/A
2d=r
R2=2ω
 Resistance is the capacity of a conductor to obstruct the passage of an electric current through it. It is controlled by the interaction of the applied voltage and the electric current passing through it.
Conductors have very little resistance, whereas insulators have a significant amount of resistance. The resistance increases as the current flow decreases. Resistance is influenced by the properties and dimensions of the material (area of cross section)
To know more about  resistance visit : brainly.com/question/14547003
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