Problem applying Newtons third law

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SUMMARY

The discussion centers on the application of Newton's Third Law in a scenario involving two skaters pulling on a rope. Each skater, with a mass of 70 kg, experiences a tension force of 35 N due to the rope, leading to an acceleration towards each other. The correct time for the skaters to meet, calculated using the equations of motion, is 5.5 seconds, as confirmed by multiple contributors. The confusion arose from differing interpretations of force distribution, but the consensus is that each skater experiences the full 35 N force individually.

PREREQUISITES
  • Understanding of Newton's Third Law of Motion
  • Basic knowledge of force, mass, and acceleration (F=MA)
  • Familiarity with kinematic equations, specifically D= T x init. Veloc. + 0.5 AT²
  • Concept of tension in a rope during dynamic motion
NEXT STEPS
  • Study the implications of Newton's Third Law in various physical systems
  • Explore kinematic equations in more complex scenarios
  • Learn about tension forces in different contexts, such as pulleys and inclined planes
  • Review examples of force interactions in real-world applications
USEFUL FOR

Students studying physics, educators teaching mechanics, and anyone interested in understanding the practical applications of Newton's laws in dynamic systems.

Neil Melnick
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Homework Statement


Two people each with a mass of 70kg are wearing in line skates and holding opposite ends of a 15m rope. One person pulls forward on the rope by moving hand over hand and gradually reeling in more of the rope. In doing so, he exerts a force of 35N (backwards) on the rope. This causes him to accelerate toward the other person. Assuming that the friction on the skaters is negligible, how long will it take for them to meet? Explain.

Homework Equations


F=MA and D= T x init. Veloc.+ 0.5 AT²

The Attempt at a Solution


Book says 7.7, I say 5.5. Book splits the 35N between the two masses, I say equal and opposite means 35N acts on each. Consulted with several engineers, no consensus. Help!
 
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Your answer of 5.5 seconds is correct. The tension in the rope will be 35 N. Each person is acted on by a 35 N tension force from the rope.
 
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There will be 35 N forces acting on both persons. There is no "splitting".
 
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