# Homework Help: Circular motion of a planet

1. Jan 13, 2008

### muahe

1. The problem statement, all variables and given/known data
A planet similar to the Earth has a radius 4.4*10^6m and has an acceleration of gravity of 10 m/s^2 on the planet's surface.The planet rotates about its axis with a period of 25h. Imagine that the rotational speed can be increased.
a/If an object at the equator is to have zero apparent weight, what is the new period?
b/By what factor would the speed of the object be increased when the planet is rotating at the higher speed?

2. Relevant equations

3. The attempt at a solution

I found the Velocity of the planet = 6633.25, but then i don't know what do to next. I don't understand what does " obj. has zero apparent weight" mean?
b/ i have no idea about it...

2. Jan 13, 2008

### Tom Mattson

Staff Emeritus
Regarding "zero apparent weight": Imagine you are standing on a scale. What the scale is actually reading is not your weight, but rather the normal force exerted on you by the scale. Draw a free body diagram and set up Newton's second law, and then ask yourself under what condition would that normal force drop to zero.