Need help with force of spring needed to launch mass from catapult

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Discussion Overview

The discussion revolves around calculating the spring constant required for a catapult to launch a 3kg mass at a speed of 20m/s at a 30-degree angle from the horizontal. The context includes considerations of gravitational acceleration and the distance the mass travels within the catapult.

Discussion Character

  • Technical explanation, Mathematical reasoning, Homework-related

Main Points Raised

  • One participant seeks assistance with a physics calculation involving the spring constant needed for a catapult launch.
  • Another participant asks if the original poster is familiar with energy formulas.
  • The original poster confirms familiarity with energy concepts but expresses a need for guidance.
  • A participant states that the initial spring potential energy should equal the final kinetic energy of the mass.
  • Another participant reminds that the mass is launched at an angle, indicating that gravitational potential energy also changes during the motion along the catapult.

Areas of Agreement / Disagreement

Participants appear to agree on the need to consider both kinetic and potential energy in the calculation, but the discussion remains unresolved regarding the specific calculations and implications of launching at an angle.

Contextual Notes

Participants have not fully explored the implications of the angle of launch on the energy calculations, and there may be missing assumptions regarding the spring's behavior and energy transformations.

DannyD
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Hi All

I need help with a physics calculation.

I have a mass of 3kg that has to be launched for Earth (9.81m/s^2 gravitational acceleration) at an angle of 30 degrees from horizontal from a catapult. The distance the mass can travel in the catapult is 2m.

What I need to know is what is the spring constant that the spring needs to have in order for the mass to leave the catapult at 20m/s?

Kind regards
Danny
 
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Are you familiar with the formulas of energy?
 
Yes I am. I'm currently studying mechanical engineering, my brain is just still in holiday mode, if I can be directed in the right direction that would also help a lot.

Regards
 
Spring potential initial = Kinetic final
 
Cool, thanks!
 
But don't forget that the mass is launched at an angle, not horizontally, so that in addition to the KE change, the gravitational PE of the mass also changes, during its motion along the catapult.
 

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