PHYS 17200 Lecture Notes - Lecture 11: Net Force
Document Summary
Phys 17200 - modern mechanics - lecture 11_potential energy. Delta_e(system) = w_surroundings = f_net * delta_r. W_surroundings = work done on object by objects in surroundings. Identification of the system (choosing the system can affect the work done on an object) ie. lifting a book. Delta_e(book) = delta_k + delta_m*c^2 = 0 + 0 = 0. W_surroundings = w_earth + w_hand = f_earth * delta_r + f_hand * delta_r = Delta_e(earth) = delta_k + delta_m*c^2 = 0 + 0 = 0. W_surroundings = f_earth * delta_r = 0. Delta_e(book) + delta_e(earth) -f_earthonbook * delta_r = f_hand * delta_r. Delta_e(book) + delta_e(earth) + delta_u = f_hand * delta_r. In this case the large mass of the earth meant that there was no significant contribution to u from work done by the book on the earth. In general, both objects in two-body systems system do significant work on each other. Bound state: k + u < 0.