Cracking the SAT Physics Subject Test

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.

More Work

If you look closely at this

formula, you will notice

also that you can derive

the following from it:

W = m(vfinal^2 − vinitial^2 )

In other words,

W = KEfinal − KEinitial

The energy an object possesses by virtue of its motion is therefore

defined as mv^2 and is called kinetic energy.

K = mv^2