Force Calculation: Incorrect Result

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SUMMARY

The discussion centers on the calculation of work done on a jet fighter during launch, specifically addressing an incorrect calculation of force. The correct approach involves using the equation for work, which is the change in kinetic energy, rather than calculating force directly. The kinetic energy of 4.20 x 10^7 J and the distance of 90 m were provided, leading to the conclusion that the work done by the catapult is equal to the change in kinetic energy, not the resultant force. The participant initially misapplied the formula, confusing force with work.

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  • Understanding of basic physics concepts, particularly work and energy
  • Familiarity with the formula for work: Work = Change in Kinetic Energy
  • Knowledge of force calculations in physics
  • Ability to manipulate scientific notation in calculations
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  • Review the principles of work and energy in physics
  • Study the relationship between force, work, and distance
  • Learn about kinetic energy calculations and their applications
  • Explore examples of work done in various physics problems
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This discussion is beneficial for physics students, educators, and anyone involved in mechanics, particularly those studying work-energy principles in the context of jet propulsion and related calculations.

Alexandra Fabiello
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Homework Statement
Jet fighter planes are launched from aircraft carriers with the aid of their own engines and a catapult. If in the process of being launched from rest, the thrust of a jet's engines is 2.10 * 10^5 N and after moving through a distance of 90 m the plane lifts off with a kinetic energy of 4.20 * 10^7 J, what is the work done on the jet by the catapult?
Relevant Equations
Work total = change in kinetic energy
force = change in kinetic energy / change in distance
force = 4.2e7 J/90 m = 466666.6667 N
this minus 2.10e5 = 2.57e5 N rounded
This is incorrect, so I'm probably missing a formula or something.
 
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Alexandra Fabiello said:
Homework Statement: Jet fighter planes are launched from aircraft carriers with the aid of their own engines and a catapult. If in the process of being launched from rest, the thrust of a jet's engines is 2.10 * 10^5 N and after moving through a distance of 90 m the plane lifts off with a kinetic energy of 4.20 * 10^7 J, what is the work done on the jet by the catapult?
Homework Equations: Work total = change in kinetic energy
force = change in kinetic energy / change in distance

force = 4.2e7 J/90 m = 466666.6667 N
this minus 2.10e5 = 2.57e5 N rounded
This is incorrect, so I'm probably missing a formula or something.
You are asked for the work done, not the force.
 
haruspex said:
You are asked for the work done, not the force.

Whoops, I mixed up 'change in kinetic energy' with force somehow.

Thanks, that worked!
 

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