# Stokes' law (Excess force due to the difference of the weight of the sphere and the buoyancy on the sphere)

## Description

The weight of an object is the force on the object due to gravity. Buoyancy is an upward force exerted by a fluid that opposes the weight of an immersed object. The excess force due to the difference of the weight of a spherical particle moving through a viscous fluid and the buoyancy on the particle, can be calculated by the mass density of the sphere and the fluid and the radius of the spherical particle.

Related formulas## Variables

F_{g} | The excess force (N) |

ρ_{p} | The mass density of the particle (kg/m^{3}) |

ρ_{f} | The mass density of the fluid (kg/m^{3}) |

g | Standard gravity |

π | pi |

R | The radius of the sherical particle (m) |