Asimple random sample of size n=40 is drawn from a population. the sample mean is found to be x=121.6 and the sample standard deviation is found to be a=12.5. construct a 99% confidence interval for the the population mean.

Amass weighing 16 pounds stretches a spring 8/3 feet. the mass is initially released from rest from a point 2 feet below the equilibrium position, and the subsequent motion takes place in a medium that offers a damping force that is numerically equal to 1/2 the instantaneous velocity. find the equation of motion if the mass is driven by an external force equal to f(t)=cos(2t).