Final answer:
If the net work done on an object is negative, the object's momentum decreases because negative work indicates the object is being slowed down, reducing its kinetic energy and thus its momentum.
Step-by-step explanation:
If the net work done on an object is negative, then the object's momentum decreases. This is because a negative net work implies that the work is being done against the object's motion, slowing it down. According to the work-energy theorem, negative work done on an object reduces its kinetic energy. As momentum is related to the velocity of the object (p = mv, where p is momentum, m is mass, and v is velocity), a reduction in kinetic energy indicates a reduction in velocity, and thus momentum.
When considering the connection between force and momentum, Newton's second law states that the net force on an object is equal to the rate of change of its momentum. If the momentum of an object increases, the net force acting on it is nonzero (c). Conversely, if the momentum of an object decreases, a negative net force must be acting on it (the force opposing the motion), confirming the decrease in momentum due to the negative work.