HELP!!!A problem on oscillation The problem statement, all variables and given/known data the equation of motion of an object is y(t)=2.0cos(0.5t+pi/4)meter a) Find its maximum acceleration and maximum speed, and its position at the time of these maxima. b) what is the speed of the object when it is +1.2m from its equilibrium position? c) what are the kinetic potntial and total energies at that point? The attempt at a solution a) for this part I don't reall understand what does the question mean by the maximum, is it when cos equals to 1? b) derive 2.0cos(0.5t+pi/4), which equals to -2sin(0.5t+pi/4)*0.5=-1sin(0.5t+pi/4) then plug the 1.2 into the unknown variable, which equals to -sin(0.5*1.2+pi/4)=-0.98 I don't really think it is the correct solution for this part c) I have to find out the correct v from part B and plug into both kinetic and potential energy equation, but I have one more problem here, which is how do i get mass for this question? P((1/2mv^2)i) + K(1/2mv^2)i) = P((1/2mv^2)f) + K(1/2mv^2)f) Thank you for helping me.