Find the constant c given quadratic equation F=

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SUMMARY

The discussion focuses on determining the constant c in the quadratic force equation F = (cx - 3.00x²)i, given specific kinetic energy values at two positions along the x-axis. The kinetic energy at x = 0 m is 18 J, and at x = 5 m, it is 12 J. The relationship between work done by the force and the change in kinetic energy is emphasized, leading to the formulation of a differential equation that relates force to velocity. By applying boundary conditions, participants conclude that two equations are necessary to solve for both the constant c and the integration constant.

PREREQUISITES
  • Understanding of Newton's second law (F = ma)
  • Knowledge of kinetic energy formula (KE = 1/2 mv²)
  • Familiarity with integral calculus and differential equations
  • Concept of work-energy principle in physics
NEXT STEPS
  • Study the work-energy theorem and its applications in mechanics
  • Learn about solving differential equations in the context of physics
  • Explore the relationship between force, velocity, and acceleration using calculus
  • Investigate boundary value problems in physics for better understanding of constants
USEFUL FOR

Physics students, mechanical engineers, and anyone interested in classical mechanics and the application of calculus to solve physical problems.

rockchalk1312
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A force F=(cx-3.00x2)i acts on a particle as the particle moves along an x axis, with F in Newtons, x in meters, and c a constant. At x = 0 m, the particle's kinetic energy is 18 J; at x = 5 m, it is 12 J. Find c.

F=ma
KE=1/2mv2

I guess I don't understand the relationship between force and kinetic energy...
 
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Hint: The work done by the force is equal to the change in kinetic energy.

How is Work Done by a force defined in terms of an integral?
 
F = ma = dv/dt
Use chain rule to get from dv/dt to dv/dx
Come up with the differential equation relating F(x) to v and dv/dx
Solve. This results in a constant of integration plus you will still have c in the equation.
So, need 2 equations since you have 2 unknowns. Use the given boundary conditions to solve for both constants.
 

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