- #1
Iamtoast
- 8
- 0
A simple problem: a mass of 8 kg is placed on the end of a copper wire. The wire extends a distance of 4.2 cm. Calculate the potential energy stored in the wire and the loss of potential energy of the mass.
The elastic strain energy stored in the wire = 1/2 . F . x = 1.65 J
The loss of gravitational potential energy by the mass = mgh = 3.3 J
So where has the other 1.65 J gone? In stretching, the entire wire (with the exception, presumably, of an infinitely thin cross section immediately adjoining the support) descends by varying amounts and itself loses g.p.e.. How is energy conserved? I can only conclude that the wire in descending, gains kinetic energy which is then dissipated as thermal energy. Comments please on this please especially on mechanisms involved.
The elastic strain energy stored in the wire = 1/2 . F . x = 1.65 J
The loss of gravitational potential energy by the mass = mgh = 3.3 J
So where has the other 1.65 J gone? In stretching, the entire wire (with the exception, presumably, of an infinitely thin cross section immediately adjoining the support) descends by varying amounts and itself loses g.p.e.. How is energy conserved? I can only conclude that the wire in descending, gains kinetic energy which is then dissipated as thermal energy. Comments please on this please especially on mechanisms involved.