I discussed with my students that if force remains constant and mass decreases then acceleration increases (a=F/m). I also explained that if force remains constant and mass increases, acceleration decreases. I know that there are a number of variables that play into this next situation and I did my best to explain this to my students without going further than my present knowledge will allow. I am interested to here your take on this coming question. If you hit a real golf ball and a plastic golf ball with a club with the same force, angle, etc. The plastic ball should have a higher initial acceleration, than the real golf ball because the force is the same but the mass is less. After both balls are hit the travel of the plastic ball will not go as far do to air resistance. The plastic ball will have less momentum (p=mv) due to its lower mass. Therefore the plastic golf will be effected more my an equal force delivered by air resistance. I could also talk about the time that the balls are in contact with the club and the longer contact and stored energy in a real golf ball due to its elasticity. Please if you have time give me your take and I will share it with the kids. I don't believe we would know everything about this situation unless we conduct a study.