How Do You Calculate the Normal Force on a Person in an Accelerating Elevator?

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SUMMARY

The calculation of the normal force on a person in an accelerating elevator involves understanding the forces acting on the individual. The correct expression for the normal force when the elevator is accelerating upwards is given by m(g + a), where m is the mass of the person, g is the acceleration due to gravity, and a is the upward acceleration of the elevator. Conversely, if the elevator is moving downward with an upward acceleration, the normal force is calculated as m(g - a). This analysis is essential for solving problems related to dynamics in non-inertial reference frames.

PREREQUISITES
  • Understanding of Newton's Second Law of Motion
  • Familiarity with Free Body Diagrams
  • Knowledge of gravitational force calculations
  • Basic principles of dynamics in non-inertial frames
NEXT STEPS
  • Study the derivation of forces in non-inertial reference frames
  • Learn about the implications of acceleration on normal force calculations
  • Explore examples of dynamics problems involving elevators and other accelerating systems
  • Review the concepts of resultant forces and their applications in physics
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Students studying physics, particularly those focusing on mechanics and dynamics, as well as educators seeking to explain the concepts of forces in accelerating systems.

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Homework Statement


A person of mass m is standing in an elevator of mass M. The elevator is moving downward, but has an upward acceleration of a. To an observer fixed on the Earth, the force exerted on the person by the floor of the elevator is

a. (m+M)g b. m(g+a) c. m(g-a) d. M(a-g) e. M(a+g)

Homework Equations


I think I have the Free Body Diagrams correct, but I am confused by finding the normal force on the person by the floor of the elevator.

Any help would be great. Thank you.
 
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There are only 2 forces acting on the person of mass m.
1)The downwards force of gravity (the weight of the person)
2) The upwards force due to the reaction at the floor.
If the person is accelerating upwards there must be a resultant force upwards.
Can you use 1) and 2) to write down an expression for the resultant upwards force.
Then resultant force = m x acceleration
 

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