I hope it is clearly visible.. Velocity of the center of mass of 2-ball system is - 11.54m/s. Minus indicates, velocity direction is in downward direction.
 
        
        
        
Answer:
The linear momentum is zero
Explanation:
Because 
When a rigid body is rotating about a fixed axis passing through point O, the body’s linear momentum given as L = mvG 
But VG= 0 so 
Linear momentum is zero
 
        
             
        
        
        
Use the kinematic equation: Vf=Vi+at
Then plug;
Vi=14 m/s
a=5 m/s²
t=20 s. Therefore;
Vf=14+(5*20)
Vf=114 m/s.
 
        
             
        
        
        
When an elevator is accelerating downward, the normal force is equal to mg-ma (hence you feel a little lighter when accelerating downwards)
Therefore, the upward force of the elevator floor on the person must be less than 750N
        
             
        
        
        
Answer:
Surface tension in water 
Friction between tires and pavement
Dissolution of salt in water
Explanation:
Surface tension in water: It is due to the electrostatic force of attraction (cohesive force) between water molecules.
Friction between tires and pavement: It is due to the attractive force between tires and pavement.
Dissolution of salt in water: The ions of  and
 and  separate due to the strong attraction of water molecules.
 separate due to the strong attraction of water molecules.