1. The problem statement, all variables and given/known data A 2.0kg pumpkin oscillates from a vertically hanging light spring once ever 0.65s. Write down the equation giving the pumpkin's position as a function of time, assuming it started by being compressed 18cm from equilibrium. How long will it take to get to the equilibrium position for the first time? 2. Relevant equations y=Acos(2πt/T) 3. The attempt at a solution The equation I got was y=0.18mcos(2πt/0.65s), which is correct according to the answer in the back of the book, but I am having trouble finding the time. What I did to find the time was to consider the object at the beginning of the motion, that is t=0 and y=.18m. So to solve for t, I divided by the 0.18m or A : y/A=cos(2πt/T) From here I used the arccos function to get the t variable out of the cosine function and got: arccos(y/A)=2πt/T Then I multiplied by T and divide by 2π to get Tarccos(y/A)/2π=t But the answer I get from this is not correct, something like 0.33s when it should be something like 0.16s.