Continuous push

From Eduwiki

By: Arpa Ghazarian

The Continuous Push p-prim is related to the notion of force as a mover. It is the idea that some naïve physicists hold that a motion is a result of some external feature or external force pushing things to move even after contact with the source of the motion had ended. It is the description of force working approximately like the scientific view of momentum. A continuous push is seen to maintain motion at a constant speed - it does not imply acceleration (unlike Newton's Law).

In the continuous push view, a force needs to be applied to an object by an external agent in order to maintain the object’s motion. Once the external agent provides the necessary push for motion, the object can use its internal force (impetus) to continue moving. This internal force is the continuous push of the external agent.

One example would be rolling a ball across the floor. A naïve physicist recognizes correctly that a push is needed (externally, like the use of one’s hand) to get the ball moving. They attribute motion directly to the push and they attribute no motion or loss of motion directly to the removal of the external force. Once the ball starts moving, it continues to roll because of the ball’s own internal force.

Another example would a naïve physicists view of pushing a cup across a table at a constant speed. They infer that the hand is what’s causing the cups motion. Thus, they interpret motion as a result of the pushing and do not recognize that a friction force balancing it.

What about gravity? Newtonian physics recognizes the force on a falling object as a continuous push - but this results in acceleration. So this is a situation where the p-prim is a productive tool for thinking.