Hysteresis energy loss in rubber

Steps:

• The stretching curve shows work input to extend the cord, area under it equals total energy supplied.
• The contraction curve shows work output as the cord retracts, area under it equals recovered energy.
• Shaded area between curves is difference: input work minus output work, representing net energy loss.
• In rubber, this loss occurs via internal friction, dissipated as thermal energy during the cycle.

Why B is correct:

• Hysteresis loop area equals energy dissipated as heat per cycle, per thermodynamics of viscoelastic materials.

Why the others are wrong:

• A: Elastic potential energy is reversible storage under the average curve, not the loss between them.
• C: Stretching work is full area under stretching curve, including both stored and lost energy.
• D: Contraction work is area under contraction curve, the recovered portion only.

Final answer: B