Suppose an object’s initial velocity is 10 m/s and its final velocity is 4 m/s. Mass is constant. What can best be concluded about the object based on the work-energy theorem? A. Work is positive, the environment did work on the object, and the energy of the system increases. B. Work is positive, the object did work on the environment, and the energy of the system increases. C. Work is negative, the object did work on the environment, and the energy of the system decreases. D. Work is negative, the environment did work on the object, and the energy of the system decreases.

Explanation:

"Work is negative," the correct answer is, "the object did work on the environment, and the system's energy declines."

In fact, the work-energy theorem states that work done is equal to kinetic energy variation:

where W represents labor, Kf represents final kinetic energy, and Ki represents starting kinetic energy. Because the kinetic energy is proportional to the velocity v,

Since the final velocity is less than the initial velocity, the work is negative (the system's kinetic energy is reduced).

This also implies that the thing worked on the environment: in reality, by working, the object gave some of its kinetic energy to the environment, resulting in a decrease in kinetic energy.

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