What force propels the runner forward?

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SUMMARY

The force that propels a runner forward is the force of friction exerted by the ground on the person, specifically option c). The normal force, which is the force exerted by the ground on the person, does not contribute to forward motion. This distinction is rooted in Newton's Third Law, where the action of the runner pushing against the ground results in a reaction force that is frictional in nature, enabling forward propulsion. Understanding the roles of these forces is crucial for analyzing motion in physics.

PREREQUISITES
  • Understanding of Newton's Third Law of Motion
  • Basic knowledge of forces: normal force and friction
  • Familiarity with free body diagrams
  • Concept of motion in physics
NEXT STEPS
  • Study the principles of friction in physics
  • Learn how to draw and interpret free body diagrams
  • Explore Newton's Laws of Motion in greater detail
  • Investigate the effects of different surfaces on frictional force
USEFUL FOR

This discussion is beneficial for physics students, educators, and anyone interested in understanding the mechanics of motion and the forces involved in running.

JessicaHelena
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Homework Statement



A person is running on a track. Which of the following forces propels the runner forward?
a) The normal force exerted by the ground on the person
b) the normal force exerted by the person on the ground
c) the force of friction exerted by the ground on the person

2. Homework Equations

none?

The Attempt at a Solution


I had thought it was a bc since the person pushes on the ground the ground pushes back by Newton's 3rd law, but the answer is c) and I'm not quite sure why — what makes normal force and force of friction different so that only one of them propels the person forward?
 
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JessicaHelena said:
I had thought it was a bc since the person pushes on the ground the ground pushes back by Newton's 3rd law, but the answer is c) and I'm not quite sure why — what makes normal force and force of friction different so that only one of them propels the person forward?
Draw a diagram of the running shoe on the ground with arrows representing the different forces.
 

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