physics of running

what we will be talking about...

General Overview

• we are going to be explaining the five forces that act between the ground and the runner, the three forces that act solely upon the runner and how newtons third law is incorporated.

Also we will be talking bout how gravity acts with a runner and how ground reaction force works with the runner.

ground reaction force works with and helps the runner.

• is a reaction force
• it is produced when the sprinters foot interacts with the track
• this occurs while some or all of the body is accelerating

Ground Reaction Force

5 forces acting between

ground and runner

the weight force : the runners mass multiplied by g

the force by the ground : equal to the magnitude to the weight force - but the opposite direction

the friction force by the running surface : parallel to the ground/runner and acts in the opposite of direction of motion

Normal force by ground : equal and opposite force of the weight force

Normal force by air : parallel to runner but can be in left or right direction

frictional force

• force acts parallel to the runner in opposite direction
• it depends on how the track and runner foot interact and the normal force ( force acting perpendicular to the surface which ground exerts) between them
• as sprinting developed, runners have learned how to use these forces to their advantage
• one force being gravity

around a track

while running around a track:

• just like any object in circular motion a runners net force and acceleration are center seeking ( piovting away from the center point)
• this happens while the runners velocity is perpendicluar to the center seeking

law of action-reaction and GRF

• this law states newtons third law
• the ground reaction force is the oppostie of the action produced by the runners foot interacting with the track.
• ground rection represents the reaction of the track to the acceleration of the center mass of the sprinter

Newton's third law with GRF

• the way runners propel themselves is newtons third law
• the normal force by feet and ground create an equal and opposite force to propel the runner forward
• for the runner to move, the runners push force must be longer in magnitude then in air force (if in opposite direction of the runner) and of friction force
• with increase in air resistance, the runner has to work harder to go the same speed

How newtons third law is incorporated

• Propulsion- force applied by muscles for a forward motion causing acceleration
• Wind- force by wind can cause acceleration or deceleration depending on direction
• Drag- force of air resistance, causing deceleration

Forces that act solely on the runner

gravity can be used as a tool while running

• leaning forward lets your body weight force pull you downward, making running, especially sprinting easier.
• gravity helps with hills by leaning forward you let gravity pull your body down the hill so your muscles are doing less work to move forward

How Gravity is incorporated

• force of gravity is the force exerted between two masses of different sizes
• smaller mass is attracted to larger i.e: world is larger mass and we are smaller masses
• gravity pulls us to earth, which is why we dont float up into space
• runners use gravity to their advantage, to use gravity runners lean forward
• leaning allows gravity to pull the runner forward and make leg work easier
• if runner develops the proper lean ( from ankles, not waist) he or she will be able to run faster and easier

How gravity affects running

• Hakala, Bailey. “The Physics of Running.” Prezi.com, 5 June 2015, prezi.com/rs48wusjo2jn/the-physics-of-running/.

• “Physics Of Running.” Real World Physics Problems, www.real-world-physics-problems.com/physics-of-running.html.

• physicstt.tripod.com/id9.html.

Bibliography