Physics

Speed is how fast something moves and has only magnitude, while velocity is speed together with a direction, making it a vector. A car going 60 km/h has a speed, but 60 km/h north is a velocity. This means an object moving at constant speed around a circle has continuously changing velocity.

Kinetic energy is the energy of motion, given by ½mv², while potential energy is stored energy due to position or configuration, such as gravitational potential energy mgh. Energy can convert between the two, for example as a falling object trades height for speed. Both are measured in joules (J).

Newton’s second law states that the net force on an object equals its mass times its acceleration (F = ma). It means a larger force produces greater acceleration, while a more massive object accelerates less for the same force. Force is measured in newtons (N), where 1 N = 1 kg·m/s².

SI units are the International System of Units, the standard set used in science for consistency. The seven base units include the metre (length), kilogram (mass), and second (time). Other quantities are derived from these, such as the newton for force and the joule for energy.