The force F accelerates the object until it reaches a critical speed proportional to F, which the object maintains afterwards whether or not the force is still applied. A long-range force must be transmitted by a medium such as a rope connecting object and agent. Therefore, long-range forces cannot act on an object in a vacuum. An impetus can be imparted by an applied force and transmitted from one object to another. An impetus may wear out or build up in the same way as the effect of an applied force.
Resistance opposes an applied force or consumes the impetus of a moving object.
Obstacles may redirect or stop motion, but they cannot be agents of an applied force. Gravity is a tendency of objects to fall down. In this conception, gravity is not necessarily a force. Nevertheless, the causal principles for applied forces which we quoted above may be attributed to gravity as well. As we saw in our discussion of Aristotelian physics, an important consequence of those principles is the belief that heavier objects fall faster.