Removing the summation signs in equation (52) in order to restrict its application to two points and dividing by the common time interval during which the respective small displacements ds and ds were made, it becomes Pdsfdt = Rds/dt, that is, Pv = Rv, which shows that the force ratio is the inverse of the velocity ratio.
The hay fever season is a common time for asthma to get worse.
This is the most common time for serious symptoms to appear such as confusion, poor coordination and sensory disturbances.