Answer:
Alternating
Explanation:
It is alternating because it is easy to distribute long distance.
Direct current is found in batteries and have large voltage drop over distance.
 
        
                    
             
        
        
        
Answer: a boy jumping down
 
        
             
        
        
        
Answer:
what this please be clear 
 
        
             
        
        
        
Answer:
  y = -19.2 sin (23.15t) cm
Explanation:
The spring mass system is an oscillatory movement that is described by the equation
       y = yo cos (wt + φ)
Let's look for the terms of this equation the amplitude I
      y₀ = 19.2 cm
Angular velocity is
      w = √ (k / m)
      w = √ (245 / 0.457
      w = 23.15 rad / s
The φ phase is determined for the initial condition   t = 0 s
,  the velocity is negative v (0) = -vo
The speed of the equation is obtained by the derivative with respect to time
      v = dy / dt
      v = - y₀ w sin (wt + φ)
For t = 0
      -vo = -yo w sin φ
The angular and linear velocity are related v = w r
       v₀ = w r₀
       v₀ = v₀ sinφ
       sinφ = 1
       φ = sin⁻¹ 1
       φ = π / 4    rad
Let's build the equation
       y = 19.2 cos (23.15 t + π/ 4)
Let's use the trigonometric ratio π/ 4 = 90º
       Cos (a +90) = cos a cos90 - sin a sin sin 90 = 0 - sin a
        y = -19.2 sin (23.15t) cm