Hi. I have a couple of physics questions and I don't know where to begin:

1. Earth's radius is 6.38 times 10 to the 6th power m and it completes one revolution every day. What is the tangential speed of a person standing on the equator?

2. Earth circles the sun at a distance of 1.50 times 10 to the 11 power m. What is the magnitude of the centripetal acceleration of Earth in its orbit?

I feel like there is a constant that I don't have to solve the equation. Any help is greatly appreciated. Thanks!!

To calculate the tangential velocity of things that go in circles (like the person standing on the equator in problem 1), use: v = \omega \cdot R, where \omega is the rotational velocity in radians/sec and R is the radius of the earth. So for the first problem you need to determine the rotational speed of the earth in radians/sec. You know it's 1 revolution per day, or 2\pi radians/day, so convert that to radians/sec and multiply by the radius of the earth in meters to get the tangential velocity in meters/sec.

For the second problem, you should know that the centripetal acceleration is calculated from a=R \cdot \omega ^2. So here you need to determine \omega for the earth in its orbit in radians/sec, square that, and multiply by the radius of the orbit to get acceleration in meters per second squared.