(a) The momentum of a particle is given by the product of its mass and velocity. For particle P, the momentum is:

\(\text{Momentum of } P = 0.2 \times 2 = 0.4 \text{ kg m s}^{-1}\)

(b) Using the conservation of momentum, the total momentum before the collision is equal to the total momentum after the collision. Initially, only P is moving, so the initial momentum is:

\(0.4 = 0.2 \times 0.3 + 0.5v\)

Solving for \(v\):

\(0.4 = 0.06 + 0.5v\)

\(0.34 = 0.5v\)

\(v = \frac{0.34}{0.5} = 0.68 \text{ m s}^{-1}\)