Special Relativity: Mass and Energy Flashcards
(8 cards)
What equation expresses the equivalence of mass and energy in special relativity?
E=mc²
Where: E is energy, m is mass, c is the speed of light in a vacuum.
What happens to an object’s mass when energy is transferred to or from it?
Transferring energy to an object increases its mass. Transferring energy from an object decreases its mass.
What is relativistic mass and how is it calculated?
Relativistic mass increases with speed and is calculated by: m = m₀ / √(1 - v²/c²)
Where: m is relativistic mass, m₀ is rest mass, v is the object’s velocity, c is the speed of light.
Why is classical kinetic energy inaccurate at high speeds?
Because classical kinetic energy, 1/2 mv², assumes constant mass. At relativistic speeds (above ~0.1c), the mass increases significantly, so this formula underestimates actual kinetic energy.
What does the kinetic energy vs speed graph show about classical vs relativistic energy?
The classical KE curve diverges from the observed relativistic KE curve at high speeds. The relativistic KE increases more rapidly, reflecting increasing mass.
How is the total energy of a relativistic object calculated?
Eₜ = m₀c² / √(1 - v²/c²)
This accounts for both rest energy and relativistic effects due to motion.
How do you calculate kinetic energy from total and rest energy?
Eₖ = Eₜ - E₀
Where: Eₜ is total energy, E₀ = m₀c² is rest energy, Eₖ is kinetic energy.
At what speeds do relativistic effects become significant in physics?
When an object moves at speeds greater than 1/10th the speed of light (v > 0.1c), classical mechanics fails to accurately describe motion and relativistic equations must be used.
