Provides some background for this problem. a ball is thrown vertically upward, which is the positive direction. a little later it returns to its point of release. the ball is in the air for a total time of 7.70 s. what is its initial velocity? neglect air resistance.

Aspring is used to stop a 50-kg package which is moving down a 20º incline. the spring has a constant k = 30 kn/m and is held by cables so that it is initially compressed 50 mm. knowing that the velocity of the package is 2 m/s when it is 8 m from the spring and neglecting friction, determine the maximum additional deformation of the spring in bringing the package to rest.