The woman is correct because it is the pace he is moving not walking.
Let us first know the given: Tennis ball has a mass of 0.003 kg, Soccer ball has a mass of 0.43 kg. Having the same velocity at 16 m/s. First the equation for momentum is P=MV P=Momentum M=Mass V=Velocity. Now let us have the solution for the momentum of tennis ball. Pt=0.003 x 16 m/s= ( kg-m/s ) I use the subscript "t" for tennis. Momentum of Soccer ball Ps= 0.43 x 13m/s = ( km-m/s). If we going to compare the momentum of both balls, the heavier object will surely have a greater momentum because it has a larger mass, unless otherwise the tennis ball with a lesser mass will have a greater velocity to be equal or greater than the momentum of a soccer ball.
Power is the rate at which work is being done.
The kinetic energy of an object is given by:

where m is the mass of the object and v its velocity.
The car in this problem has a mass of m=600 kg and a velocity of v=10 m/s, therefore if we put these numbers into the equation, we find the kinetic energy of the car: