Impulse and Net Force Equations

AI Thread Summary
The discussion centers on formulating a net force equation for a falling elastic object, specifically a spring, during a collision with the ground. The net force equation is expressed as N - W - kx, where N is the normal force, W is the weight, and kx represents the spring's compression. A key question raised is whether there exists a point where N equals W + kx, suggesting a state of equilibrium. However, the notion of equilibrium is challenged, as maintaining rest for any duration seems implausible given the dynamic nature of the spring's force. The conversation emphasizes that while the mathematical aspects can be straightforward, the conceptual visualization of the problem is more complex.
lehel
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I have a problem in trying to express a net force equation for a falling elastic object when collision ensues.

For instance, you drop a spring with a spring coefficient k. the spring compresses a distance x after a time t for a maximum time of tf and distance xf. the spring has a weight W. during the collision, the ground creates a normal force N which is the result of impulse.

thus, calling the direction upward the positive y-axis, the net force on y = N - W - kx. My question is, what does the net force along y equal? Actually, my real question is if there is a point where N = W + kx. But even if at a certain point there is no total accerlation, you would have an equilibrium equation would you not? Isn't that impossible because if the spring was in equilibrium for even a fraction of time dt, wouldn't it stay at rest?
 
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You are better attempting this question with the work-energy theorem. Because the force of spring changes over time, integration will be needed.

The maths is the easy part, visualizing the problem is were the work is.
 
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