Wkb Chapter 6c

Doing Energy Problems: A Summary

Like real Estate: The RBD is Location, how you got there is of no interest.

The System in which energy is added, subtracted, or altered, is equally important.

Kinds of energy

K = (1/2) mv² = kinetic energy = energy of motion

PE_g = U_g = mgy = gravitational potential energy = energy due to position

PE_s = U_s = (1/2)kx² = spring potential energy = energy due to compression or extension of a spring.

W = work done on the system (positive work), or by the system (negative work) that enables us to arrive at the final location.

DU_int = F_k Dx =change in internal energy of the system, heated up (positive DU_int) or cooled down (negative DU_int)

DU_int will be negative in the initial position if the surface is not included in the system.

DU_int will be positive in the final position if the surface is included in the system.