# Homework Help: The earth takes exactly 24 hours for one full rotation calculate

1. Jun 25, 2012

### sazzy

the speed of rotation of a point on the equator

the title is the only information I have been given to work out this questions and it relates to a2 phyics uniform circular motion and the answer is 465ms-1 I just cannot get it I know the eqautor must have something to do with it PLEASE HELP

the textbook gives equations speed = 2pi*r/T but I am not given radius and using the radius does not give the correct answer anyway

the closest I got was 471 ms-1 using pi/24*3600 and I just used pi because I am assuming because it asks along the equ I should use 180 degrees

2. Jun 25, 2012

### gbaby370

If you're getting 471, it could just be a matter of how you're rounding some of the variables like pi or the radius of the Earth.

I used the exact same equation using the pi option on my calculator and for r, I used 6.378x10^6 and I got 463.82m/s.

Hope this helps!

3. Jun 25, 2012

### D H

Staff Emeritus
The Earth takes 24 hours to make a full rotation with respect to the Sun. The Earth is also orbiting the Sun. This means it takes a bit less than 24 hours for that Earth to make a full rotation with respect to the stars. Another way to look at it is that the Earth rotates a bit more than 360 degrees in 24 hours. This extra little bit of rotation is what gives that answer of 465.1 m/s as opposed to the 463.8 m/s that gbaby370 obtained.

4. Jun 25, 2012

### SammyS

Staff Emeritus
Hello sazzy. Welcome to PF.

Look up the radius of Earth.

Using that, you can find circumference of Earth, which is the distance that a point on the equator travels in one day.

The number of seconds in one day is 24*3600.

If you want to divide some number by 24*3600, you should put (24*3600) in parentheses.

When you computed π/24*3600, that was equivalent to 3600*π/24 . It's just a coincidence that this gave a result that's close to the correct answer.