Mechanics

5 articles

The Science Behind the "Dropping" Sensation During Velocity Changes

The sensation of being pulled backward during acceleration or thrown forward during sudden braking is not caused by a mysterious force, but is the result of inertia—an inherent property of all objects with mass.

2 min read2

Mechanics

Why don’t we feel Earth’s rotation?

Each morning, the Sun does not actually "rise" from the horizon. Instead, Earth’s rotation carries our location into the sunlit region. At the equator, the planet’s surface moves at approximately 1,670 km/h, faster than most commercial aircraft. Why, then, do we not perceive this motion, and why are we not flung into space?

2 min read3

Mechanics

Waves: Wavelength, Frequency, Amplitude

A wave carries energy, not matter. This article defines the four quantities behind every periodic wave — wavelength, frequency, period and amplitude — then uses them to separate mechanical waves from electromagnetic ones, and transverse waves from longitudinal ones, following BIPM, NASA and USGS.

2 min read8

Mechanics

Mass, Inertia and Weight

Mass and inertia are two ways of describing one property; weight is a force, measured in newtons, that changes with where you stand. This article sets the three quantities side by side as NIST and BIPM define them, explains why "weightless" does not mean gravity is gone, and why the equality of inertial and gravitational mass remains an open question.

2 min read5

Mechanics

Newton's Three Laws of Motion

Kepler said how the planets move; Newton said why. This article gives the three laws as NASA renders them from the Principia, the rigorous form of the second law (force as the rate of change of momentum), the point where the third law is most often misread, and the range over which the three laws still hold.

2 min read5