Chapter 3, Problem 1RCQ

As you read this in your chair, how fast are you moving relative to the chair? Relative to the Sun?

To determine

The speed of the person sitting on the chair relative to the chair and relative to Earth.

Answer to Problem 1RCQ

Solution:

Relative to the chair, the speed is zero.

Relative to the Sun, the speed is $\text{1}0\text{7}000\text{ km}/\text{hr}$.

Explanation of Solution

Given Info: A person sitting on chair.

When we describe motion, we describe it relative to some other reference object.Since the person is sitting on the chair, and is not moving relative to the chair, therefore the relative speed of the person with respect to the chair is zero.

Average distance between Sun and Earth is $r=\text{1496}00000\text{ km}$.

Distance by Earth in a year $D=2\pi \times r$

Plugging the values in the above equation

$D=2\pi \times 149600000\text{km}$

The speed of Earth relative to the Sun is calculated as

$\frac{2\pi \times 149600000}{365\times 24}=107000\text{km/hr}$

This is the speed of the Earth when it moves around the Sun. If a person is sitting on the chair, it can be said that he is on Earth. So, he will also have the same speed as that of the Earth, therefore the relative speed of the person with respect to the Sun is $\text{1}0\text{7}000\text{ km}/\text{hr}$.

Conclusion:

The relative speed of the person with respect to chair is $0$.

The relative speed of the person with respect to Sun is $\text{1}0\text{7}000\text{ km}/\text{hr}$.