The boy’s foot causes the motion. His foot is the one that causes the ball to roll down the hill.
        
             
        
        
        
Answer:
I think it has to do something with their ionizations... not entirely sure though.
Explanation:
 
        
             
        
        
        
Answer:
(B) the sum total of all matter and energy
Explanation:
Universe comprises of all the matter and energy that exists in space. It contains billions of stars, planets and interstellar matter that is clouds of dust and gas. There is large amount of the empty space in between. 
Universe contains stars as many as grains of sand on all beaches on the Earth. These stars are grouped into galaxies. Milky Way is one of the galaxies.  Galaxies can be grouped into clusters and super-clusters.
 
        
             
        
        
        
Answer:
v = 14.32 m/s
Explanation:
According to the principle of conservation of linear momentum, both the momentum and kinetic energy of the system are conserved. Since the two balls are in the same direction of motion before collision, then;
 +
 +  = (
 = ( +
 +  ) v
) v
0.035 × 12 + 0.120 × 15 = (0.035 + 0.120) v
0.420 + 1.800 = (0.155) v
2.22 = 0.155 v
⇒ v = 
       = 14.323
The velocity of the balls after collision is 14.32 m/s.
 
        
             
        
        
        
Answer:
Difference in experimental data.
Explanation:
There is difference of experimental value between the experiment that is performed on the earth and on the international space station because presence of gravity. The result of the experiment on the earth is different due to the presence of gravity that contributes in the result of the experiment as compared to international space station where no gravity is present so there is high difference of the numerical value of the result of both experiments of earth and international space station.