Answer:
Explanation:
A vector is parallel to the y axis . 
Let its magnitude be A . So the vector can be represented as A j .
where i and j are unit vectors in x and y axis direction . 
The x component of A j will be dot product of A j with i 
The x component of A j = A j . i 
= A x 0      [  Since j . i = 0 ] 
= 0 
 
        
             
        
        
        
The block moves with constant velocity: for Newton's second law, this means that the resultant of the forces acting on the block is zero, because the acceleration is zero.
We are only concerned about the horizontal direction, and there are only two forces acting along this direction: the force F pushing the block and the frictional force 

 acting against the motion. Since their resultant must be zero, we have:

The frictional force is

where

 is the coefficient of kinetic friction

 is the weight of the block. 
Substituting these values, we find the magnitude of the force F:
 
 
        
        
        
The climate<span> was generally warmer and more humid than today, probably because of very active volcanism associated with unusually high rates of seafloor spreading. 
</span><span>The first placental mammals appeared at the beginning of the Cretaceous. The Cretaceous saw the rise and extinction of the toothed birds, Hesperornis and Ichthyornis. The earliest fossils of birds resembling loons, grebes, cormorants, pelicans, flamingos, ibises, rails, and sandpipers were from the Cretaceous.</span>
        
                    
             
        
        
        
I remember c/d. That's not a problem. But if you want 'c', you'll have to give me 'd'.
        
             
        
        
        
Angle, θ2 at which the light leaves mirror 2 is 56°
<u>Explanation:</u>
Given-
θ1 = 64°
So, α will also be 64°
According to the figure:
α + β = 90°
So,
β = 90° - α
   = 90° - 64°
   = 26°
β + γ + 120° = 180°
γ = 180° - 120° - β
γ = 180° - 120° - 26°
γ = 34°
γ + δ = 90°
δ = 90° - γ
δ = 90° - 34°
δ = 56°
According to the law of reflection, 
angle of incidence = angle of reflection
θ2 = δ = 56°
Therefore, angle θ2 at which the light leaves mirror 2 is 56°