Ch 8 Potential energy and Conservation of energy

Conservative force 以下兩個情形和力是不是保守有什麼關係？ Fig. 8 -2： a tomato is thrown upward –

Conservative force & nonconservative forces • 什麼是保守力？什麼是非保守力？請各舉出三種 path independence Fig. 8 -4 Fig. 8

Potential Energy (§ 8 -4) • △U = -W (8 -1) (8 -5) (7

Potential Energy (§ 8 -4) • gravitational potential energy 令 yi=0時，Ui=0 U(y)= mgy (8

Gravitational Potential energy Fig. 8 -29 Ch 8, Problem 2 & 10 Fig. 8

§ 8 -5 Conservation of mechanical energy Work －kinetic energy theorem △K= Kf -

Potential energy Curve Checkpoint 4 畫出 F(x)-x 的圖 Ch 8, Problem 71

Ch 8, Problem 38 The potential energy of a diatomic molecule (a two-atom system

Potential energy Curve sample problem 7 -7 • 畫 U(x)-x 關係圖，從x=17 mm到x= -17 mm

Potential energy Curve • Emec • Turning points • Equilibrium points • Stable Equilibrium

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Ch 8 Potential energy and Conservation of energy

Conservative force 以下兩個情形和力是不是保守有什麼關係？ Fig. 8 -2： a tomato is thrown upward – kinetic energy & work – potential energy & work Fig. 8 -3： a block attached to a spring

Conservative force & nonconservative forces • 什麼是保守力？什麼是非保守力？請各舉出三種 path independence Fig. 8 -4 Fig. 8 -5

Potential Energy (§ 8 -4) • △U = -W (8 -1) (8 -5) (7 -32) 定義位能： (8 -6) • System (two or more objects) • Conservation force • gravitational potential energy U(y)= mgy (8 -9) • elastic potential energy U(x)= (1/2) k x 2 (8 -11)

Potential Energy (§ 8 -4) • gravitational potential energy 令 yi=0時，Ui=0 U(y)= mgy (8 -9) • elastic potential energy 令 xi=0時， Ui=0 U(x)= (1/2) k x 2 (8 -11)

Gravitational Potential energy Fig. 8 -29 Ch 8, Problem 2 & 10 Fig. 8 -34 Ch 8, Problem 8 , 20, 26 Ch 8, Problem 89, 95 Fig. 8 -33 Ch 8, Problem 7, 21

§ 8 -5 Conservation of mechanical energy Work －kinetic energy theorem △K= Kf - Ki =W Potential energy and work (8 -18)

Potential energy Curve Checkpoint 4 畫出 F(x)-x 的圖 Ch 8, Problem 71

Ch 8, Problem 38 The potential energy of a diatomic molecule (a two-atom system like H 2 or O 2) is given by where r is the separation of the two atoms of the molecule and A and B are positive constants. This potential energy is associated with the force that binds the two atoms together. (a) Find the equilibrium separation, that is, the distance between the atoms at which the force on each atom is zero. Is the force repulsive (the atoms are pushed apart) or attractive (they are pulled together) if their separation is (b) smaller and (c) larger than the equilibrium separation?

Potential energy Curve sample problem 7 -7 • 畫 U(x)-x 關係圖，從x=17 mm到x= -17 mm • 寫出 U(x) 和 F(x) 的關係 • 把物體拉到 x=12 mm處放手，畫出彈簧的機械能 • 把物體拉到 x=8 mm處放手，畫出彈簧的機械能 • Turning points U(x) • Equilibrium points F(x) x -17 -12 12 17 x

Potential energy Curve • Emec • Turning points • Equilibrium points • Stable Equilibrium • Unstable Equilibrium Fig. 8 -32：Ch 8, Problem 5 & 11 Fig. 8 -10(c)