A student hits a rolling bowling ball with a mallet and the bowling ball speeds up. Another student claims that the student broke the law of conservation of momentum because the bowling ball gained momentum. Which of these is the best explanation of why the law is not broken?
1) The law of conservation of momentum only applies to isolated systems, and the student and the bowling ball are not isolated.
2) The law of conservation of momentum only applies to objects at rest, and the bowling ball was already in motion.
3) The law of conservation of momentum only applies to objects of equal mass, and the student and the bowling ball have different masses.
4) The law of conservation of momentum only applies to objects in a vacuum, and the student and the bowling ball are in air.