Calculating velocity based on applied force If I have a block sitting on a spring, ignoring air resistance, with 45N of stored elastic energy in the spring, and the block weighs 500g, what would be the process for calculating its maximum height? I know how to solve this if I know the initial upward velocity of the block, but I don't know how to calculate the initial velocity if I know the force applied. This is also assuming a virtually perfect environment without the effects of air-resistance or other impacts. The travel distance of the spring is 0.3 meters with a spring constant of 100N/m.
 A: Actually this seems pretty simple, if you have 45N stored in the spring - this is the force that will be applied to the block when it is launched (assuming perfect perfectness perfection) from there you simply need your Second Law of motion, which states that the force is equal to the mass times the acceleration. From here you have your acceleration, at this point it is a simple problem of motion, i am not certain how it is worded in english but it should be something like "Gradually Decreasing Motion" - the kind of motion that gradually loses velocity, since the acceleration from the spring is driving the block upwards, but the Earth's gravity is pulling it downwards.
Easy-peasy. :)
A: You can actually use the conservation of energy principle to solve this.Account for the initial energy of the system...initially the potential energy of the system is 45 J + the potential energy of the block with respect to the earth and equate it to the final energy I.e. The kinetic energy and the potential energy. 
