What's better.....being faster or being slower? Obviously faster. Have you ever wondered why some people are faster than others though? Are there trends?
To understand the basics physics of running, you can think of your arms as pendulums. A pendulums velocity depends on the length of the pendulum, not the mass of the bottom. If the pendulum is shorter, the speed of the mass at the bottom is faster. Your mass at the end of the pendulum you can think of as your feet. Then proceed to assume that your legs are the pendulums. In order to shorten the pendulum...you have to bend your knees. Obviously you cannot run well with your knees locked, but you will run faster if your knees are bent.
You can also think of your arms as a second type of pendulum. If you bend your arms at a 90 degree angle and swim them in stride with your legs, you will then proceed to run even faster.