Wize High School Grade 12 Physics Textbook > Foundations / Introduction / Measurement
Inertial Reference Frames
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Inertial Reference Frames
In the Universe, everything is in constant motion. The Earth is rotating at approximately 1,700 km/hr, and it is rotating around the Sun at approximately 30km/s. When we describe an object on Earth moving at 100km/hr we are ignoring the absolute velocity that it actually has and comparing it relatively to the seemingly stationary nature of Earth. This is what's known as relative motion.
Generally, we discuss motion in Physics that is relative to the surface of the Earth, when this assumption is applied we are applying an Inertial Reference Frame. We are assuming that the Earth is stationary and describing motion on Earth relative to the surroundings.