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: 12 N to the right
Explanation:
If we calculate the net force acting on the box, we will have:
<u>In y-component:</u>
(1)
Where 
is the Normal force, directed upwards and 
is the weight of the box (gravity force), directed downwards.
(2)
(3) Hence the net force in the vertical component is zero
<u>In x-component:</u>
(4)
Where 
and 
(5)
(6) This is the net force in the horizontal component
Therefore, the total net force acting on the box is 12 N directed to the right
Vx=cos60(4)
x-component of velocity
If you think about it, it makes a right triangle when you combine all the different types of forces together such as v, vx and vy. Then, you can use trigonometry and soh cah toa in order to figure out vx.
