QUESTION #678

# Why are left turns on a cycle easier than right? Also, when I run track I notice that everyone always runs counterclockwise.

Asked by: Robert Crosby

### Answer

Interesting question. In theory, turns on a cycle should be equally strenuous. However, you are most-likely right handed. This means that your right arm is probably a bit stronger than your left arm, so pushing the handlebar forward with your right arm might be a bit easier than with your left. On multi-lane roads, left turns are not as sharp as right turns are, so on a motorcycle, this effect is augmented by the fact that sharper turns require more force on the handlebars to execute. The fact that everyone runs counterclockwise is almost certainly cultural. In the United States, people drive in a counterclockwise way on the outside of a curving path. Since a track looks like the "outside" of a path, running that way is probably habit. I'd be curious to see if people run clockwise in England and other countries where people drive on the opposite side of the street. Perhaps that can be my question!
Answered by: David Consiglio, B.S., High School Chemistry and Physics Teacher

Left turns versus right turns on a bicycle or on a track have nothing to do with the physics of the situation. If that were true, clocks would run the other way, and English style cars would be more efficient than American cars because the empty side is on the left. None of these things is true. The real reason that it's "easier" is because most people are right-handed (including you, probably). Most right-handed people feel more comfortable extending their right hands. They like to put their right foot forward, because most are right-footed as well. When you lean left to make a turn, the opposing force that keeps you upright pushes to the right. You maintain your balance by pushing down on the bicycle harder or softer... with your right foot. Since your right foot is more responsive, and more practiced... it "feels" easier to turn that way. When you turn right, your left side is controlling things, and your left side is a little slower, a little stiffer, and it just doesn't "feel" as comfortable. You waste energy fighting the uncertainty in your non-dominant side. That's why it's "easier" to turn one way or the other... because you're more accustomed to using one side, which makes it feel more comfortable.
Answered by: Frank DiBonaventuro, B.S., Air Force Officer, Physics Grad, The Citadel

Even though i ride a bike every day, it'd never occurred to me that it was easier to make a left turn than a right turn, but thinking about it now, i'd have to agree. I suspect that its to do with most people having a stronger right side to their body, an in particular a stronger right leg. When making a left turn, the bike leans to the left, as does your lower body. This creates an angle between the wheels and the road, which is what creates the turning force. However, your upper body leans the opposite way to balance the bike. Note: This actually increases your angular momentum and the centripetal force required to turn the bike, but is a necessity for two wheeled vehicles. Racing drivers (of cars) actually lean into the corner to increase their turning ability. This means the weight of our upper body is roughly above your right pedal and can be used to assist the push from your right leg but not your left. Your right leg therefore does more of the work and so it is helpful if that is your stronger leg.
Answered by: Stuart Taylor, Chemistry Graduate Student, Oxford University, UK