Ch. 12 Energy il Potential energy Ch 12 Energy II: Potential energy
Ch.12 Energy II: Potential energy Ch. 12 Energy II: Potential energy
12-1 Conservative forces(保守力) Kinetic energy <> velocity Potential energy? It is defined only for a certain class of forces called conservative forces What are conservative forces Do spring force, gravitational force, and frictional force et al. belong to conservative forces? Ch 12 Energy II: Potential energy
Ch.12 Energy II: Potential energy 12-1 Conservative forces(保守力) Potential energy? It is defined only for a certain class of forces called conservative forces. Do spring force, gravitational force, and frictional force et al. belong to conservative forces? Kinetic energy Velocity What are conservative forces?
1.The spring force Fig 12-1 (a) Fig11-13 0000 Relaxed length )100000000 00 d 00000 (e) k( The total work done by the spin force is zero in the process from(a) to(e) (round trip Ch 12 Energy II: Potential energy
Ch.12 Energy II: Potential energy 1. The spring force Fig 12-1 x 0 0 d d -d (a) (b) (c) (d) (e) ( ) 2 1 2 2 s f i W = − k x − x o x Relaxed length Fig 11-13 The total work done by the spin force is zero in the process from (a) to (e) (round trip). 0 0
2. The force of gravity See动画库/力学夹/2-04功的计 算举例(2) The total work done by the gravity is zero during the round trip If the gravitational force is not constant. is there still such behavior of the work Ch 12 Energy II: Potential energy
Ch.12 Energy II: Potential energy The total work done by the gravity is zero during the round trip. 2. The force of gravity If the gravitational force is not constant, is there still such behavior of the work? See 动画库/力学夹/2-04功的计 算举例 (2)
3. The frictional force See动画库/力学夹/204功的计 算举例(1) The total work done by frictional force is not zero in a round trip. Ch 12 Energy II: Potential energy
Ch.12 Energy II: Potential energy 3. The frictional force The total work done by frictional force is not zero in a round trip. See 动画库/力学夹/2-04功的计 算举例 (1)