SACE Stage 2 Physics Practice Exam 2026 - Free Physics Practice Questions and Study Guide

The Lorentz factor is a crucial concept in the theory of special relativity introduced by Albert Einstein. It describes how time, length, and mass are affected as an object's speed approaches the speed of light. The Lorentz factor is specifically defined by the equation γ (gamma) = 1 / √(1 - v²/c²), where v is the object's velocity and c is the speed of light in a vacuum.

As an object's speed increases, the Lorentz factor increases, leading to significant relativistic effects. Time dilation occurs, meaning that time appears to pass slower for the moving object relative to a stationary observer. Length contraction occurs, where the object appears shorter in the direction of its motion to an outside observer. Additionally, there is an increase in relativistic mass, which impacts how the object behaves under acceleration.

This understanding explains how an object's characteristics change dramatically at relativistic speeds, making the second choice the correct one. The other options do not accurately capture the essence of the Lorentz factor: changes in weight due to gravity relate more to general relativity, variations in the speed of light pertain to its constancy under different conditions, and energy emission by rapidly moving objects is not directly described by the Lorentz factor itself.