# What force propels the runner forward?

• JessicaHelena
In summary, a person running on a track is being propelled forward by the force of friction exerted by the ground on the person. While the normal force exerted by the person on the ground and the normal force exerted by the ground on the person may cancel each other out, it is the force of friction that provides the necessary propulsion. This can be seen through a diagram of the running shoe on the ground, where arrows representing the different forces show that the force of friction is the only force acting in the direction of motion.
JessicaHelena

## 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?

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.

## 1. What is the force that propels a runner forward?

The force that propels a runner forward is known as the propulsive force, which is generated by the muscles in the legs.

## 2. How does the body generate the force to move a runner forward?

The body generates the force to move a runner forward through a combination of muscle contractions, joint movements, and the transfer of energy from the ground to the body through the feet.

## 3. Are there any external forces that contribute to a runner's forward movement?

Yes, there are external forces that contribute to a runner's forward movement, such as air resistance and gravity. However, the propulsive force generated by the body is the primary force driving the runner forward.

## 4. How does running technique affect the propulsive force?

Running technique can have a significant impact on the propulsive force. Proper running form, including a strong push off the ground with each step and efficient use of leg muscles, can increase the propulsive force and ultimately improve a runner's speed and efficiency.

## 5. Can the propulsive force be increased through training?

Yes, regular training and conditioning can increase the propulsive force generated by the body. This can be achieved through strength training exercises that target the leg muscles used in running, as well as drills and techniques that improve running form and efficiency.

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