[Physics] Where does the energy required to stop a moving body come from and go

energymomentumnewtonian-mechanics

For a long time, I have been thinking about this: In order to stop a moving body, I have to apply impulse to change the existing momentum to $0$. For the impulse I have to impart force on the moving body . That means I have to eliminate all the kinetic energy associated with the moving object in order to bring it to a halt. Thus, work is done on the object, right? If work is done, energy must be given by me…

Here is where my confusion arises:

  1. If I eliminate the associated kinetic energy of the body, where does this energy go?
  2. The work(?) done by me on the moving object to stop it obviously uses energy from me. Again, where does this energy go?

Best Answer

Thus, work is done on the car, right?

No, the car does (positive) work on whatever is stopping it.

Alternatively, you could say that negative work is done on the car, but still, the meaning is the same: the car loses energy and something else gains that energy. What that something else is, and what type of energy it gains, depends entirely on how the car is stopped.