With these physics questions (11-15)

Give one example to show that when substances are mixed,it may result in a chemical or a physical change depending on the conditions.

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.

Which describes increasing the efficiency of energy resource