Answer to Question #169115 in Mechanics | Relativity for Scott

Question

A horseshoe is heated in a blacksmith's furnace until it glows blue/white. Does the mass of the horseshoe change? If so, explain how and why. b) If a spring is stretched to twice its equilibrium length, has the spring's mass been altered in the process? If so, explain how and why.

Answer 1

A. No. Heating the horseshoe only increases the vibrational kinetic energy of the atoms which leads to expansion and emittance of visible light. These are only energy-energy interactions. No mass is lost and no mass-energy conversion is taking place. Hence, the total mass of the horseshoe remains constant.

B. No, the stretching of the spring only changes the configuration of the system increasing the inter-atomic distances which increases the restoring force that tends to pull it back. The work done in the spring gets stored as elastic potential energy. There is hence no reason why mass would change.