Please can someone help by answering these questions asap. A cow has eaten 1500KJ of stored chemical energy in the form of food. 945KJ is excreted as waste products. 495KJ is 'used' for respiration.

a. How much of the original 1500KJ is stored as chemical energy in the tissue of the cow?
b. The answer to part a is all the energy that can be transferred to a human. Calculate the efficiency of the energy to the human. ​

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.