newton

Meaning: The newton (N) is the SI unit of force. One newton is the net force that gives a 1 kg mass an acceleration of 1 m/s², so 1 N = 1 kg·m/s². It is a derived unit built from the base units kilogram, meter and second. For scale, an object of about 0.1 kg weighs roughly 1 N near Earth's surface. Weight, tension, normal force, friction and electric force are all measured in newtons.

Equation: F = ma, where F is net force in newtons (N = kg·m/s²), m is mass in kilograms (kg) and a is acceleration in m/s². For weight, W = mg, where g ≈ 9.8 m/s² near Earth's surface.

On the MCAT: Expect unit checks by dimensional analysis: pressure in pascals is N/m², and work in joules is N·m, so 1 J = 1 N·m. Calculations ask for force from a given mass and acceleration, or for weight from a mass. Masses given in grams must be converted to kilograms before the result comes out in newtons.

Common confusion: Students treat newtons as if they measured mass. Kilograms measure mass, which stays the same wherever the object is. Newtons measure force, and weight is a force. A 10 kg object weighs about 98 N near Earth's surface, and its mass is still 10 kg elsewhere, though its weight differs.