4. The height of an helicopter is given with an equation of y=3t². An object is dropped from the helicopter at t = 2s. a) How long does it take to reach the ground? b) Calculate its velocity when it hits the ground. c) Calculate its acceleration. 5. The position of an object moving in a straight line is given by x(t)=t3 - 2t² a) b) What is its average velocity for the interval from t = 3s to t = 4s? What are its instantaneous velocities at t = 3s and t = 4s? c) d) What is its average acceleration for the interval from t = 3s to t = 4s? What is its instantaneous acceleration at t = 3s and t = 4s? e) Is there ever a time when acceleration is zero?