Eugenia and David pull on each other: Observational Experiment

Aim

To construct a relation/rule relating the force Eugenia exerts on David and the force David exerts on Eugenia when either one of them pulls the rope.

Prior Knowledge

• Kinematics: position, velocity and acceleration.
• Graphing skills.
• Newton's first law.
• Newton's second law.
• Reference frames.

Description of the Experiment

• Carefully observe what happens when David pulls on Eugenia and Eugenia pulls on David.
• Does it seem possible for David to pull on Eugenia without starting to move himself? Does it seem possible for Eugenia to pull on David without starting to move herself?

Addtional Information

Eugenia's mass with gear:	52kg
David's mass with gear:	83kg





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Questions

For one particular trial when either David pulls or Eugenia pulls:

• Decide what you need to measure to determine the speed of Eugenia and the speed of David after the pull is over.
• After the speeds have been determined, can you find the acceleration of David and the acceleration of Eugenia?
• What assumptions should you make in order to find their accelerations during the time interval when the pull was exerted?
• Use the information you have found and previously established relation between acceleration and the net force to compare the forces they exert on each other.
• Repeat for the other trials
• What can you conclude about the strength of the pull of David on Eugenia as compared to Eugenia's pull when Eugenia pulls on David?
• What can you conclude about the strength of the pull of Eugenia on David as compared to David's pull when David pulls on Eugenia?