Question

Which explanation describes the forces involved for a person to walk down the sidewalk?
A.
The person's feet push backward on the sidewalk; the sidewalk pushes forward on the person.
B.
The person's feet push forward on the sidewalk; the sidewalk pushes forward on the person.
C.
The person's feet push backward on the sidewalk; the sidewalk pushes backward on the person.
D.
The person's feet push forward on the sidewalk; the sidewalk does not push on the person.

Answer 1

A.

When you walk you push your foot backward against the sidewalk. By static friction the sidewalk pushes your foot forward with an equal and opposite force (Newton's third law), giving you the forward push to move.