## SAT Physics Subject Test

**Chapter 4 ****Work, Energy, and Power**

**KINETIC ENERGY**

Consider an object at rest (*v*_{0} = 0), and imagine that a steady force is exerted on it, causing it to accelerate. Let’s be more specific; let’s say that the object’s mass is *m*, and let **F** be the force acting on the object, pushing it in a straight line. The object’s acceleration is **a** = **F**/*m*, so after the object has traveled a distance ∆*s* under the action of this force, its final speed, *v*, is given by Big Five #5:

But the quantity **F**∆*s* is the work done by the force, so *W* = *mv*^{2}. The work done on the object has transferred energy to it, in the amount *mv*^{2}.

The energy an object possesses by virtue of its motion is therefore defined as *mv*^{2} and is called **kinetic energy**.

*K* = *mv*^{2}