The height of a helicopter above the ground is given by h = 3.15t^3, where h is in meters and t is in seconds. At t = 2.10 s, the helicopter releases a small mailbag. How long after its release does the mailbag reach the ground?

A bullet is fired straight up in the air at an initial speed of 245 m/s. After how much time is the bullet at a height of 10.1 X 10^2 m and heading down?

During the time interval 0 < t < 1, the velocity of an object as a function of time is v = 5 + 3t^2 + 2t^3. Knowing that the object follows a rectilinear trajectory, What is the correct expression for the acceleration?

The height (in meters) of a projectile shot vertically upward from a point 4 m above ground level with an initial velocity of 25.5 m/s is h = 4 + 25.5t − 4.9t2 after t seconds.  When does the projectile meet its maximum height and what is its maximum height?