Force in Physics
Definition of force
To study dynamics we must have a definition of force. Everyone has a feeling what force is, but a “feeling” is not sufficient to build a precise definition.
Forces can cause motion, but they are not always correlated with motion. The pull of gravity on a parked car does not cause motion. There are hundreds of object around us on which forces are acting, but which are not moving.
Newton stated that
change of motion is caused by forces.
In other words
force is “something” which can change the state of motion.
By state of motion we understand parameters defining the motion, that is
direction
velocity
acceleration
We will return to this definition after presenting all three of Newton’s Laws of Dynamics. Then it will be easer to understand what force really is.