Final answer:
In an elastic collision, both momentum and kinetic energy are conserved. The initial velocity of mass A is 5 m/s.
Step-by-step explanation:
In an elastic collision, both momentum and kinetic energy are conserved. Let's denote the initial velocity of mass A as v and the final velocity of mass B as vB. Since both objects have equal mass, the principle of conservation of momentum states that the total momentum before the collision equals the total momentum after the collision:
mass A * initial velocity of A + mass B * initial velocity of B = mass A * final velocity of A + mass B * final velocity of B
mass A * v + mass B * (-v) = mass A * (-v) + mass B * vB (substituting the given values)
v = 5 m/s (solving for v)
Therefore, the initial velocity of mass A is 5 m/s.