Solving Dave's Cardboard Contact Force Problem

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Homework Help Overview

The problem involves a scenario where a person, Dave, drops onto cardboard boxes, and the discussion centers around the forces involved in his fall and the resulting contraction of the boxes. The subject area includes concepts from mechanics, specifically kinematics and forces.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants explore the relationship between the equations of motion and the directions of displacement. There is a discussion about the appropriateness of using delta x versus delta y in the context of the problem. Some participants question the application of gravitational force and its role in the equations.

Discussion Status

The discussion is ongoing, with participants offering insights into the equations and their applications. There is recognition of the complexity in applying the concepts of force and motion, and some guidance is provided regarding the need to clarify the acceleration and initial conditions.

Contextual Notes

Participants note the challenge of reconciling different equations for horizontal and vertical motion, as well as the implications of using gravity in the calculations. There is also mention of the need to understand the initial conditions of the problem better.

capridece
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Hi this is a problem from my midterm at the beginning of the quarter and i have a final coming up so i need to know the previous midterm material but i still don't understand this one question.

Dave suddenly drops from the wire and lands at a velocity of 2m/s on some cardboard boxes that contract to absorb the force of his fall. If the cardboard boxes exerts a force of 350N on Dave who weighs 70kg, how much do the cardboard boxes contract?


the equation i would use is v^2=vo^2 - 2adelta y

but in her solutions she shoes delta x. Why is it delta x if the cardboard is going to be contracting in the y direction?

If someone can help me start off this problem i will so grateful!
 
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Off the top of my mind, I think her equations are supposed to be general. You can substitute delta y for delta x. If you continue on with that assumption, does it get you the right answer?
 
yeah that's what i thought too but there are two equations, one for x and one for y and they differ.

v^2 = Vo^2+2adelta x

v^2 = Vo^2-2gdelta y

in x you add, in y you subtract
 
That's general kinematics. You can't just plug in the exact numbers for the exact equations and hope for the best. At what rate is David accelerating when he jumps off? I assume that his initial vertical v is zero. If you figure that out, you can find the unknown y.
 
nvm i think youre right. It was just difficult for me to apply the force and the mass to the equation. I thought gravity would be used instead.
 

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