Explanation:
It is given that,
The Displacement x of particle moving in one dimension under the action of constant force is related to the time by equation as:

Where,
x is in meters and t is in sec
We know that,
Velocity,

(a) i. t = 2 s

At t = 4 s

(b) Acceleration,

Pu t = 3 s in the above equation
So,

Hence, this is the required solution.
Answer:
The mass of the products and reactants are the same on both sides of the equation.
The number of atoms of products and reactants are equal and hence it proves the law of conservation of mass.
.