Answer and Explanation:
This experiment is known as Lenz's tube.
The Lenz tube is an experiment that shows how you can brake a magnetic dipole that goes down a tube that conducts electric current. The magnet, when falling, along with its magnetic field, will generate variations in the magnetic field flux within the tube. These variations create an emf induced according to Faraday's Law:

This emf induced on the surface of the tube generates a current within it according to Ohm's Law:

This emf and current oppose the flux change, therefore a field will be produced in such a direction that the magnet is repelled from below and is attracted from above. The magnitude of the flux at the bottom of the magnet increases from the point of view of the tube, and at the top it decreases. Therefore, two "magnets" are generated under and above the dipole, which repel it below and attract above. Finally, the dipole feels a force in the opposite direction to the direction of fall, therefore it falls with less speed.
 
        
                    
             
        
        
        
Answer: energy 
Explanation: So the input and output of the power grid system is energy.
 
        
                    
             
        
        
        
Answer:
1.65
Explanation:
The equation of the forces along the horizontal direction is:
 (1)
 (1)
where
F = 65 N is the force applied with the push
 is the frictional force
 is the frictional force
m = 4 kg is the mass 
 is the acceleration
 is the acceleration
The force of friction can be written as  (2), where
 (2), where
 is the coefficient of kinetic friction
 is the coefficient of kinetic friction
R is the normal force exerted by the floor
The equation of forces along the vertical direction is
 (3)
 (3)
since the bookcase is in equilibrium. Substituting (2) and (3) into (1), we find

And solving for  ,
,

 
        
             
        
        
        
Answer:
51793 bright-dark-bright fringe shifts are observed when the mirror M2 moves through 1.7cm
Explanation:
The number of maxima appearing when the mirror M moves through distance \Delta L is given as follows,

Here,
 = is the distance moved by the mirror M
= is the distance moved by the mirror M
 is the wavelenght of the light used.
 is the wavelenght of the light used.
 = 0.017m
= 0.017m



Therefore, 51793 bright-dark-bright fringe shifts are observed when the mirror M2 moves through 1.7