15. A travelling wave is described by the equation y(x, t)= 0.003 cos (20 x + 200t) where y and x are measured in meters and t in seconds. What is the period of this wave?

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.