# Determine the centripetal force

1. Oct 1, 2008

### xxgaxx

1. The problem statement, all variables and given/known data
Assume that the standard kilogram would weigh exactly 9.8 N at sea level on the earth's equator if the earth did not revolve about its axis. then take into account the fact that the earth does rotate so that this mass moves in a circle of radius of 6.4 * 10^6 meters at a constant speed of 465 meters/sec. a) determine the centripetal force needed to keep the standard moving in its circular path. and b) determine the force exerted by the standard kilogram on a spring balance from which it is suspended at the equator. (e.g. its weight)

known: r=6.4 * 10^6 m, v=465 m/s

2. Relevant equations
a=v^2/r
F=ma
I don't know part b

3. The attempt at a solution
a) a=v^2/r=(465 m/s)^2/ (6.4 * 10^6 m)=0.033785 m/s^2
F=ma=(i don't know what m is?) (0.033785 m/s^2)

2. Oct 1, 2008

### cepheid

Staff Emeritus
You don't know what the mass of something that's being used as the standard for the kilogram is?

3. Oct 1, 2008

### xxgaxx

what would i use for my value of m?