Question

What forces are being used when walking a dog and how ?

Answer 1

There are tons of forces that balance out on your body while you walk. Subsequent physics classes will tell you about each and how they are represented. Here are a few in order of how people usually learn them.

Gravity: The earth exerts a gravitational force on each particle in your body that has mass. Overall, this can be represented as a single force that pulls directly toward the center of the earth from the point called your center of mass.

Normal Force: The contact between your feet/shoes and the ground exerts a force normal (straight out from) the ground. If you are on flat ground, this force is directly opposite the force of gravity, and in most cases will be equal to it such that you have no vertical net force.

Friction: Friction between your shoes/feet and the ground, pointing parallel to the ground and in the direction of your walking motion creates the force necessary for you to move. The microscopic peaks and valleys of the ground and your feet/shoes create small normal forces that can sum into a direction of motion.

Air Buoyancy: Since you are in a fluid, the mass of the fluid you displace creates an upward force away from the center of the earth. Since the density of air is miniscule, this force is generally neglected except in the most precise of circumstances.

Drag and Air resistance: While you walk, as you move through a fluid, that fluid exerts friction on your body in the form of drag. It is usually small unless you’re moving very fast relative to the fluid.

Air pressure, blood pressure, body tensions: Your body has a balance of blood pressure, muscle tensions, which oppose outside air pressures which equalize out to form the shape your body is in.

Internal forces: Many forces act within you such as air pressure, other muscle tensions, and internal stresses which balance out. Usually in physics these are lumped under internal forces.