Question

Two cannonballs are floating in space: one is ice-cold and the other is red-hot. Compare how they
react when pushed on by identical forces.

Answer 1

Ice cold object is at 0 ⁰C (=273 K) temperature and red hot object is at very higher temperature than ice cold object. From Stephen-Boltzmann law emitted radiation per unit are per unit time is directly proportion to fourth power of temperature and hence red hot object has very high emission of black body radiation. This radiation exerted pressure along normal of its flow. This is why, when same amount of force is exerted on ice cold object and red hot object, red hot object's displacement is less than ice cold object. Radiation pressure oppose external force.

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