Yes, our friend is right, because there is no contradiction to the law of conservation of mass in the above equation. It just the mass of the product is equal to the mass of reactants.. and that is shown in the equation you have presented earlier 
 
        
             
        
        
        
Answer:
I am not really sure, but it is probably Carbon Dioxide
Explanation:
 
        
                    
             
        
        
        
Answer:
Fighting
Explanation:
Fighting with someone like punch for punch can make the person bleed which an injury to the guy who you fought with and you can be arrested if the parents file a complain at the police station
 
        
                    
             
        
        
        
Answer:
The momentum of an object is defined as the mass of the object times the velocity of the object, as P = m*v.
So the equipment needed would be:
Something to measure the mass of the object, like a balance.
Something to measure the speed of the object, like a doppler radar, or a simpler thing may be a cronometer, with that you can measure the amount of time that the object needs to travel a given distance, and with that you can obtain the speed of the object.
Now you can notice that speed is different than velocity, this is true, velocity is a vector, so this has a direction, then you need something to fix the direction in which the object moves, in this way you can determine the velocity.