# Why does a sprinter running in a 200 m event lean towards the centre of the curve he is rounding?

Jan 27, 2018

So that less distance is covered.

#### Explanation:

When they lean towards the centre of the curve, they will cover less distance in total, which therefore makes it faster to reach till the end.

As they get closer and closer to the centre, they cover less and less distance, and therefore they will want to get as close as possible to the centre, while still being on the track.

Jan 27, 2018

Leaning toward the center of the curve provides balance of torques on the sprinter.

#### Explanation:

A body in motion tends to continue in motion, in a straight line, unless acted on by an outside force. Newton's 1st Law

A body moving in a circle must therefore have a force on it continually causing the change in direction. This force is called centripetal force (centripetal means toward the center). The sprinter needs to change course, turning to follow the curve. Friction between their feet and the ground provides the centripetal force. However, the sprinter's center of mass is some distance above the feet, and that is a problem.

Assume the sprinters run the course in a counterclockwise (or anticlockwise) direction. The friction, trying to accelerate the sprinter toward the center of the curve, provides a clockwise torque (as viewed from behind) which would tend to make the sprinter fall toward the outside of the curve -- unless some way to counter that torque with an equal and opposite torque were found.

When the sprinter leans toward the center of the curve, the force of the sprinter's weight is still a vertical force and it points to a spot on the ground toward the center compared to where the feet are. That provides a counterclockwise torque to oppose the clockwise torque that following the curve generates.

I hope this helps,
Steve