A rock is dropped straight down from roof. It hits the ground with a velocity of 28.2 m/sec. How high was the roof, and how long did it take to hit the ground?

What are the necessary conditions for fusion?

Current from a charged capacitor lights a bulb. as time goes on the brightness of the

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.