When does a falling object reach terminal velocity?

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 backward on the person. b. the person's feet push forward on the sidewalk; the sidewalk does not push on the person. c. the person's feet push backward on the sidewalk; the sidewalk pushes forward on the person. d. the person's feet push forward on the sidewalk; the sidewalk pushes forward on the person.

What makes thermal imaging cameras useful? they can detect differences in color. they can detect differences in wave speeds. they can detect differences in temperature. they can detect mechanical waves.

Wavelength of 125 meters is moving at a speed of 10 m/s. what is it's frequency?