Relative Motion

This week in physics we learned about relative motion.  We already knew that all motion is relative, meaning when observing the motion of something; we must ask ourselves what it is moving relative to. Relative motion is the calculation of the motion of an object with regard to some other moving object. When calculating the velocity of the motion of an object, we do not measure the velocity relative to the ground, but to another moving object.

The picture below is of my friend Kainalu at ILH Champs Cross Country race last week. Lets say for example he and the Punahou guy right behind him are both running at 10mph. If this were the case, they would both not be moving relative to each other. However, if Kainalu were to accelerate to 12mph, relative to the other runner, he would be moving away. Also, relative to Kainalu, the other runner would be moving backwards, even though he is remaining at the same speed. Relative to the other runner, Kainalu would be running at +2mph. Relative to Kainalu, the other runner would be running at -2mph.