Answer:
A fast feather 
Explanation:
The faster any item is, the more momentum it has
 
        
                    
             
        
        
        
An Active solar energy system because it uses the sun to heat up the green house an I’m return the plants grow an produce food
        
             
        
        
        
Answer:
  K_a = 8,111 J
Explanation:
This is a collision exercise, let's define the system as formed by the two particles A and B, in this way the forces during the collision are internal and the moment is conserved
initial instant. Just before dropping the particles
           p₀ = 0
final moment
           p_f = m_a v_a + m_b v_b
           p₀ = p_f
           0 = m_a v_a + m_b v_b
tells us that
           m_a = 8 m_b
          
            0 = 8 m_b v_a + m_b v_b
            v_b = - 8 v_a                    (1)
indicate that the transfer is complete, therefore the kinematic energy is conserved
starting point
            Em₀ = K₀ = 73 J
final point. After separating the body
           Em_f = K_f = ½ m_a v_a² + ½ m_b v_b²
            K₀ = K_f
            73 = ½ m_a (v_a² + v_b² / 8)
            
we substitute equation 1
            73 = ½ m_a (v_a² + 8² v_a² / 8)
            73 = ½ m_a (9 v_a²)
            73/9 = ½ m_a (v_a²) = K_a
             K_a = 8,111 J
 
        
             
        
        
        
The best option is C. This is due to friction.