Momentum
The kinetic energy of an object does not depend on the direction it is moving: it is just a number. There is a different quantity, momentum, that depends on direction. It is defined as the product of mass and velocity, and has an associated direction, just like velocity itself. Then another statement of the Law of Inertia is that in the absence of external forces, the momentum of an object is constant. Massive objects and rapidly moving objects have large momentum: they will be difficult to stop. Similarly we could describe the trajectory of a thrown baseball by saying that the thrower gives the ball momentum that determines its initial path, from which it is gradually deflected by the force of gravity.