Kinetic Energy Basics

Kinetic energy is the energy of motion.

An object that has motion – whether it is vertical or horizontal motion – has kinetic energy. There are many forms of kinetic energy – vibrational (the energy due to vibrational motion), rotational (the energy due to rotational motion), and translational (the energy due to motion from one location to another).

If we want to accelerate an object, then we must apply a force. Applying a force requires us to do work. After work has been done, energy has been transferred to the object, and the object will be moving with a new constant speed. The energy transferred is known as kinetic energy, and it depends on the mass and speed achieved.

Kinetic energy can be transferred between objects and transformed into other kinds of energy. For example, a flying squirrel might collide with a stationary chipmunk. Following the collision, some of the initial kinetic energy of the squirrel might have been transferred into the chipmunk or transformed to some other form of energy.

How to calculate kinetic energy?

To calculate kinetic energy, we follow the reasoning outlined above and begin by finding the work done W, by a force F, in a simple example. Consider a box of mass m being pushed through a distance d along a surface by a force parallel to that surface. As we learned earlier

W=F⋅d=m⋅a⋅d

we can substitute the acceleration if we know the initial and final velocity vi and vf—as well as the distance.