Solving Catapult Project: Finding Spring Constant

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SUMMARY

The discussion centers on calculating the spring constant for a catapult project using Hooke's Law. The user determined a spring constant of 68.346 N/m based on an arc length and a force of 4.2 N at 36 degrees, while another group reported a significantly lower value of 2 N/m. The confusion arises from whether to use the average force or the difference between the forces of 4.2 N and 1.4 N. Clarification on the correct methodology for applying Hooke's Law is needed to resolve the discrepancies in the spring constant calculations.

PREREQUISITES
  • Understanding of Hooke's Law and its application in spring mechanics
  • Knowledge of force measurements and their implications in physics
  • Familiarity with basic trigonometry, particularly in relation to angles and forces
  • Ability to calculate arc length in relation to angular displacement
NEXT STEPS
  • Review the principles of Hooke's Law and its application in real-world scenarios
  • Learn how to accurately calculate arc length based on angle and radius
  • Investigate methods for averaging forces in elastic systems
  • Explore experimental techniques for measuring spring constants in various setups
USEFUL FOR

Students in physics or engineering courses, educators teaching mechanics, and hobbyists working on catapult or spring-based projects.

Chloers
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I'm doing a catapult project but I'm sort of confused.
I need to find the spring constant in order to get the elastic potential energy.
The force of pulling back the catapult lever to 36 degrees above the horizontal is 4.2 N. Right before the lever is at rest, 90 degrees, the force is 1.4 N.
One of my lab partners got the force average as 6.68 N.
My teacher told me to use the arc length as the x in the equation.
When that was plugged into the equation I got 68.346 N/m as the spring constant. Does that make sense? I asked another group and they got a spring constant of about 2 N/m.

I know I am suppose to use Hooke's Law but am I suppose to use the average force or the difference of the forces?

What am I doing wrong?
 
Last edited:
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Without a sketch and other additional information, I think it is impossible to tell.
 

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