Переклад текст на українську мову newton's analysis of motion is summarized in his famous "three laws of motion". in his great work, the principia (published in 1687), newton readily acknowledged his debt to galileo. in fact, newton's first law of motion is very close to galileo's conclusions. it states that: every body continues in its state of rest or of uniform speed in a straight line unless acted on by a nonzero net force. the tendency of a body to maintain its state of rest or of uniform motion in a straight line is called inertia. as a result, newton's first law is often called the law of inertia. newton's first law does not hold in every reference frame. for example, if your reference frame is fixed in an accelerating car, an object such as a cup resting on the dashboard may begin to move toward you (it stayed at rest as long as the car's velocity remained constant the cup accelerated toward you but neither you nor anything else exerted a force on it in that direction. in such an accelerating reference frame, newton's first law does not hold. reference frames in which newton's first law does hold are called inertial reference frames (the law of inertia is valid in them). for most purposes, we can usually assume that reference frames fixed on earth's rotation, but usually it is close enough.) any reference frame that moves with constant velocity (say, a car or an airplane) relative to an inertial frame is also an inertial reference frame. reference frames where the law of inertia does not hold, such as the accelerating reference frame discussed above, are called noninertial reference frames. how can we be sure a reference frame is inertial or not? by checking to see if newton's first law holds.