## Physics Technology Update (4th Edition)

Imagine a rock sliding across the floor during a hurricane. The normal force and the weight of the rock equal out to give a zero y-component of force. There may be a force applied from the wind to slide the rock, but drag or friction can equal out with the force of the wind to leave a zero x-component of the force. Since force is equal to $F=ma$ and $F=0$, the acceleration must be zero. Since $a=\frac{\Delta v}{\Delta t}$ and $a=0$, there must be no change in velocity and therefore the object can slide at a constant speed.