Energy and Power

• y(x,t)= ym sin( kx- ?t)

• uy=dy/dt= -ym ? cos( kx- ?t) (keep x fixed!)

• dK=(1/2)dm uy2 =(1/2) ?dx ?2 ym2cos2(kx- ?t)

• kinetic energy of element dx

• potential energy of a segment is work done in stretching string and depends on the slope dy/dx

• when y=A the element has its normal length dx

• when y=0, the slope dy/dx is largest and the stretching is maximum

• dU = F( dl -dx) force times change in length

• both KE and PE are maximum when y=0

Previous slide

Next slide

Back to first slide

View graphic version