- #1
SteelDirigibl
- 40
- 0
Ok I have most of this solved but can't get the third part right.
A spring of spring constant 128N/m is compressed a distance of 2.0m from its equilibrium position, and used to project a ball of mass 4.0 kg directly upwards. Neglect air resistance.
1. What is the potential energy of the spring in its compressed position? 256 J
2. To what maximum height above its initial (compressed) position does the ball reach? 6.53m
3. Earlier, just when the spring is returned to its equilibrium position, as the ball was moving upwards, how fast was the ball moving? undetermined?
KE=1/2*mv2
PE=mgh
Us=1/2kx2
The first thing I tried was simply using the previously calculated energy, 256J, and solving for velocity in the KE equation. This gets 11.3 m/s using mass of the ball, but I'm sure I'm supposed to account for some other motion of the spring, because it doesn't transfer all of that energy to the ball. The correct answer is 9.4 m/s. Where do I go from here?
Homework Statement
A spring of spring constant 128N/m is compressed a distance of 2.0m from its equilibrium position, and used to project a ball of mass 4.0 kg directly upwards. Neglect air resistance.
1. What is the potential energy of the spring in its compressed position? 256 J
2. To what maximum height above its initial (compressed) position does the ball reach? 6.53m
3. Earlier, just when the spring is returned to its equilibrium position, as the ball was moving upwards, how fast was the ball moving? undetermined?
Homework Equations
KE=1/2*mv2
PE=mgh
Us=1/2kx2
The Attempt at a Solution
The first thing I tried was simply using the previously calculated energy, 256J, and solving for velocity in the KE equation. This gets 11.3 m/s using mass of the ball, but I'm sure I'm supposed to account for some other motion of the spring, because it doesn't transfer all of that energy to the ball. The correct answer is 9.4 m/s. Where do I go from here?