Spring constant and conservation of energy

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Homework Help Overview

The problem involves a ball launcher in a pinball machine, utilizing a spring with a specified force constant. The scenario includes an inclined surface and requires determining the launching speed of a ball when the spring is released, while neglecting friction and the mass of the plunger.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the conservation of energy principle, considering the relationship between spring potential energy and kinetic energy. There are questions about the interpretation of the term "launching speed" and whether it implies a unitless answer.

Discussion Status

The discussion is active, with participants exploring the implications of the problem's wording regarding units. Some suggest focusing on energy conservation, while others express confusion about the expected format of the answer. No consensus has been reached on the interpretation of the speed requirement.

Contextual Notes

There is uncertainty regarding the interpretation of the problem's request for a unitless answer, which may affect the approach to solving the problem. Participants are also considering the effects of gravitational potential energy in the context of the inclined surface.

Knfoster
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Homework Statement


The ball launcher in a pinbgall machine has a spring that has a force constant of 36 N/cm. THe surface on which the ball moves is inclined theta=10.1 degrees with respect to the horizontal. If the spring is initially conressed 4.25 cm, find the launching speed of a .120 kg bawhen the plunger is released. Friction and the mass of the plunger e negligible.

Homework Equations



PE=.5k(xf-xi)^2
KE=.5mv^2

The Attempt at a Solution


I'not sure what launching speed is supposed to be, it supposed to be an answer that doesn't require units. Does that mean I need to be finding the spring constant? If so, do I just set the KE=PE?
 
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They give you the spring constant. 36 N/cm.

So think conservation of energy.

Spring potential depressed = kinetic energy at release point plus additional increase in gravitational potential energy at release point .
 
The force constant is the spring constant. You're looking for a velocity.

Think about it if we compress a spring at some angle we are storing potential energy in the spring, but we also have to take into account gravity, does this help?
 
It can't be simply velocity that I'm looking for because an answer not requiring units is needed. Any other ideas?
 
I'm pretty sure it's got units -- it asks for the launching speed. Speed's have units of distance per time.
 
I know... it should but, I'm doing homework through lon-capa and it's telling me that it doens't require units, so it can't be asking for velocity.
 
They ask for speed.

Calculate it as m/s.

Ignore their not asking for units.
 

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