Recall that the formula for momentum is:

To correctly calculate momentum using the formula \( P = mv \), we need to ensure both sides of the equation have consistent units and that the calculation is correct.

The formula \( P = mv \) can be used as follows:

1. Substitute the values for mass (m) and velocity (v): Given:

   • Mass (m) = 9 kg
   • Velocity (v) = 5 m/s

2. Calculate momentum (P): \[ P = 9 , \text{kg} \times 5 , \text{m/s} = 45 , \text{kg m/s} \]

The first response, "45 N = (9 kg)(5 m/s)" is incorrect because it incorrectly labels the units of momentum as newtons (N), which is a unit of force, rather than \( \text{kg m/s} \).

The second response, "4 kg*m/s = (9 kg)(5 m/s)", is also incorrect for two reasons:

1. The calculation is incorrect, as \( 9 \times 5 = 45 \), not 4.
2. The left side states 4 kg*m/s which is incorrect.

Thus, neither response correctly shows the calculation of momentum. The correct calculation using the values provided should yield:

\[ P = 45 , \text{kg m/s} \]