Answer :
Final answer:
The work done by a 60 kg object to stop, with a change in kinetic energy by -70 J, is -70 J. This is option C.
Explanation:
The question is about the work done by an object to stop, which involves a change in kinetic energy. When work is done on an object, it can either increase or decrease its kinetic energy. In this case, the object has undergone a negative work of -70 J to come to a stop.
This means the work done by the object is taking away its kinetic energy, as seen with the example of the generator doing negative work on the briefcase. The work done by the object, as it stops, is -70 J (option C).
This interpretation corresponds to the principle of conservation of energy, where energy is transferred rather than lost, just changing forms.
Thus, the correct answer is -70 J, as the applied force has acted in the direction opposite the object's motion.
