# Confusing with Relative Motion

• optoracko
In summary, the conversation discusses the concept of relative motion and how it applies to a person walking on a moving escalator. The escalator is 20.0m long and takes 50.0s to ride from bottom to top. The person's walking speed is 0.500 m/s relative to the escalator. By calculating the escalator's velocity of 0.400 m/s, it is determined that the person's walking speed would be 0.500 m/s if the escalator were not moving. The conversation also highlights how all motion is relative and that something must be stationary for relative motion to be observed.
optoracko

## Homework Statement

An escalator is 20.0m long. If a person stands on the escalator, it takes 50.0s to ride from bottom to the top.

a) if a person walks up the moving escalator with a speed of 0.500 m/s relative to the escalator how long does it take for the person to get to the top.

V = d / t

## The Attempt at a Solution

I'm not understanding relative motion too well. I begin by calculating the velocity of the escalator which is 0.400 m/s. Since the person is walking up with a speed of 0.500 m/s in relation to the escalator, does that mean that if the escalator was not there, he'd be walking at 0.500 m/s? Why would I not add the two velocities (.4 + .5) and isolate for the time?

optoracko said:
I begin by calculating the velocity of the escalator which is 0.400 m/s.
Correct.
Since the person is walking up with a speed of 0.500 m/s in relation to the escalator, does that mean that if the escalator was not there, he'd be walking at 0.500 m/s?
It is better to think of this way: It means that if the escalator were not moving, he'd be walking at 0.500 m/s.
Why would I not add the two velocities (.4 + .5) and isolate for the time?
Why do you think you should not do that?

Not quite sure. I guess I thought that if it was moving relative, it would mean that it moves that speed and the speed of the elevator. Blech.

Would that mean that anything with relative motion requires something to be stationary, such as in this question?

optoracko said:
Would that mean that anything with relative motion requires something to be stationary, such as in this question?
All motion is relative. You may think that you are at rest sitting in front of your computer reading this message, but
relative to the center of the Earth you are moving at about 1,000 miles an hour
relative to the Sun you are moving much faster
relative to a galaxy far far away much much faster.

Get the picture?

Yeah, makes sense now. Thanks!

## What is relative motion?

Relative motion refers to the movement of one object in relation to another. It is the difference in position, velocity, or acceleration between two objects.

## How does relative motion affect our perception of speed?

Relative motion can make it difficult to accurately judge the speed of an object because our perception is influenced by the movement of other objects around it. For example, a car may appear to be moving faster if it is passing by other cars on the highway, but may seem slower if it is the only car on a wide open road.

## What is the difference between relative motion and absolute motion?

Relative motion is the movement between two objects, while absolute motion is the movement of an object with respect to a fixed point or reference frame. Relative motion is dependent on the observer's frame of reference, while absolute motion is independent of any observer.

## How does relativity theory explain relative motion?

Relativity theory states that the laws of physics are the same for all observers, regardless of their relative motion. This means that the observations and calculations of relative motion will be the same for all observers, even if they are moving at different speeds.

## Can relative motion be used to calculate the position of an object?

Yes, relative motion can be used to calculate the position of an object. By knowing the relative velocity between two objects, their positions can be calculated using the laws of motion and the time elapsed. This is often used in navigation systems, such as GPS, to determine the position of a moving object.

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