Answer:
20.243 s
Explanation:
Because the escalator and person moving in the same direction, relative velocity can be calculated by summing the velocity of the escalator and velocity of the person.
The speed of escalator can be calculated as,

Relative velocity
Therefore total time required to take the person to get to the top

Helped us in modern days do to his contribution to the study of motion back in the day is what helpes us know how to study motion.
When a beam of light that is, at first, in air and oriented perpendicular to the surface of a body of water be deflected as a result of transition into water--------It does not deflect , the light direction will not change.
What happens to light when it passes through air?
All materials have what is known as an index of refraction, which is linked to how fast light can travel through the material. As light passes through air and into another clear material (such as glass), it changes speed, and light is both reflected and refracted by the glass.
How does light travel through air and water?
When light travels from air into water, it slows down, causing it to change direction slightly. This change of direction is called refraction. When light enters a more dense substance (higher refractive index), it 'bends' more towards the normal line.
Learn more about direction of beam of light:
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D. an outside or unbalanced force acts upon the object.
Answer:
A chain reaction will be sustained in a sub-critical mass.
Explanation:
Hope this helps!
If not, I am sorry.