Class 9: Conservation of Energy Class 9: Conservation of Energy - PowerPoint PPT Presentation

Class 9: Conservation of Energy Class 9: Conservation of Energy

Potential Energy on Earth Surface U(y) = mgy g y y = 0 0 You are free to choose the You are free to choose the zero level

Potential Energy of a Spherical Object Potential Energy of a Spherical Object M a m r M Mm U(r) = - G r For r >a only U( ∞ ) = 0 For r >a only. U( ∞ ) = 0

Potential Energy of a Charge Potential Energy of a Charge Q a q r 1 1 Qq Qq = U(r) πε 4 r 0 0 For r >a only U( ∞ ) = 0 For r >a only. U( ∞ ) = 0

Potential Energy of a Spring Potential Energy of a Spring Hooke’s Law: F F = ‐ kx kx U = ½ kx 2 (U at natural length = 0 ) ½ kx 2 (U at natural length U 0 )

Conservation of Energy Conservation of Energy Δ T + Δ U Δ T + Δ U = Work done by all non ‐ conservative forces.