Calculating Air Resistance in Falling Objects

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Homework Help Overview

The discussion revolves around calculating the force of air resistance acting on a falling object with a specified mass and constant velocity. The subject area includes concepts of forces, motion, and Newton's laws.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the relationship between constant velocity and acceleration, questioning the implications of zero net force. They discuss the forces acting on the object, including gravity and air resistance, and their directions.

Discussion Status

Participants are actively engaging with the concepts, clarifying the relationship between forces and motion. Some guidance has been provided regarding Newton's laws, and there is an ongoing exploration of the forces involved.

Contextual Notes

The original poster expresses uncertainty about arriving at the answer provided in the textbook, indicating a potential gap in understanding the application of the concepts discussed.

axlg38
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Homework Statement



an object with a mass of 1.21g is falling at a constant velocity of 1.1 m/s. What is the force of air resistance exerted on the object?

Homework Equations



f=ma

The Attempt at a Solution



i imagined that if the object is falling at a constant velocity, then acceleration is 0. so it seems that f=0, but that's obviously not true. i have no idea how to do this

EDIT: according to the book, the answer is about .0119N, I am not sure how to arrive at that answer
 
Last edited:
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The acceleration is 0. The velocity is constant. If by "f=0", you mean Ʃf = 0, that is correct.

[Edit: the book is correct]
 
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What are the forces acting on the falling body?
 
gravity and air resistance?
 
Yes! In which direction is gravity working? In which direction is air resistance working?
 
gravity is working downward, and air resistance is working upward
 
Right, so if acceleration is zero and Ʃf (sum of the forces) = ma = 0, what can you conclude about the magnitudes of the 2 forces?
 
They cancel each other out? i thought if that happened, the object wouldn't move at all
 
Ah, I see where you are hung up. You should review Newton's 1st law. It is okay for an object to have a constant velocity as long as there is no net force acting on it (think of an object traveling through space, away from significant sources of gravity). In this case, you correctly assert that "they cancel each other out" -- there is no net force acting on the body.

Would you say that the 2 forces are equal and opposite?
 
  • #10
yes?
 
  • #11
Yes! Then we are almost home. What is the force of gravity on the body. Please report in units of Newtons.
 
  • #12
11.858 n
 
  • #13
Almost. [Edit: I'm using "almost" in the broadest sense, meaning you could be off by 3 orders of magnitutde :smile:] Newtons are (kg*m)/s2
 
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  • #14
alright, thanks for the help haha this is going to save me on the test scheduled for tuesday
 

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