This post gives a preliminary idea of how physics fundamentals like friction and Newton’s laws of motion are involved in the design aspects of running shoes. Nowadays when sports have become so competitive, a pair of running shoes efficiently designed can bring a huge improvement in the performance of a runner. Here we will see first how Running shoes increase the force of static friction exerted by the ground on the athlete and improve his/her performance.
Running shoes increase the force of static friction exerted by the ground on the athlete – how?
- Running shoes are designed to increase the force of static friction exerted by the ground on the athlete.
- The bottom tread of the running shoe (called the outsole) is made from a durable Carbon-Rubber compound to help increase the coefficient of static friction.
- This allows the athlete to accelerate at greater rates. This design also helps when quick starts and stops are required. It also helps an athlete have greater agility.
The typical design of a running shoe is shown in Figure 1.
How does the midsole of running or sports shoes protect ankles and knees by absorbing the normal force?
- Running shoes are designed to protect ankles and knees from injuries during strenuous activities.
- They are also designed to be as light as possible to reduce weight and help increase speed.
- The midsole is made from foam to help reduce the magnitude of forces acting on the ankles and knees as a person is running.
- The inner part of the midsole is often made of a harder material to provide stability, while the outer part is made of a softer material to help cushion the impact.
- It is not unusual for the magnitude of the normal force to triple during various sports activities. The cushion helps absorb some of this impact.
- Some midsoles include air or gels to help further absorb the impacts when running.
The upper part of the shoe is designed for comfort and to decrease movement of the foot within the shoe. The heel counter is a hard cup-shaped device used to promote stability and the movement of the heel.
The forces exerted by an athlete on the ground while running can be very large in magnitude, but from Newton’s third law, a force of equal magnitude is exerted by the ground on the feet in the opposite direction. The best running shoes allow an athlete to quickly accelerate, while at the same time absorbing some of these forces to protect the athlete from injury.