86.3 Kepler's laws of planetary motion 2. Kepler’ s second law During equal time intervals the radius vector from the sun to a planet sweeps out equal areas. 86.3 Kepler's laws of planetary motion Central force--force that acts along the line between two particles F×F= rF sin丌=0 rma=0 xp)=(r×m) d dr d X(mv)+rx(m =0+rma=012 §6.3 Kepler’s laws of planetary motion 2. Kepler’s second law During equal time intervals the radius vector from the sun to a planet sweeps out equal areas. M §6.3 Kepler’s laws of planetary motion Central force—force that acts along the line between two particles r × F = rF sinπ = 0 r r r ×ma = 0 r r 0 0 ) d d ( ) ( d d ( ) d d ( ) d d = + × = = × + × × = × r ma t v mv r m t r r mv t r p t r r r r r r r r r r