Nínú fisiksi, ìtipá tabi ipá (force) ni ohun kohun to ba fun ohun agbarajo kan tikonigbekun ni imuyara. Ìtipá tun le je pipe ni iti tabi ifa to mu ki ohun kan to ni isupo lati yi iyara re pada (eyi je lati bere sini gbera lati ipo isinmi), i.e., lati muyara, tabi to le je ohun to ba de ko woara. Ìtipá ni iwon ati idojuko, eyi so fi iposi alakoja. Ofin keji Newton, F=ma, can be formulated to state that an object with a constant mass will accelerate in proportion to the net force acting upon and in inverse proportion to its mass, an approximation which breaks down near the speed of light. Newton's original formulation is exact, and does not break down: this version states that the net force acting upon an object is equal to the rate at which its momentum changes. See for example pages 9-1 and 9-2 of Feynman, Leighton and Sands (1963).