What is the Magnitude of the Third Force in a Three-Force System?

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Homework Help Overview

The problem involves a three-force system acting on an object moving at a constant velocity. Two forces are specified: one with a magnitude of 150 N along the x-axis and another with a magnitude of 100 N at a 120° angle from the x-axis. The objective is to determine the magnitude of the third force.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the implications of the object moving at a constant velocity and question the sum of the forces acting on it. There are attempts to relate the forces using trigonometric functions and the Pythagorean theorem, though uncertainty remains about the correct application of these concepts.

Discussion Status

The discussion is ongoing, with participants exploring the relationship between the forces and the conditions of constant velocity. Some guidance has been offered regarding the independence of x and y components, and the need for two equations to solve for the two unknowns.

Contextual Notes

There is mention of confusion among the class regarding the problem, indicating a potential lack of clarity in understanding the principles involved in force equilibrium.

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Homework Statement


An object that is moving at a constant speed velocity is acted upon by three forces. One force is 150 N along the x-axis, the second is 100 N along a direction making a counterclockwise angle of 120° with the x-axis. What is the magnitude of the third force?



Homework Equations


Not sure, these are the only ones I THINK are remotely relevant (but I have no idea which is why I'm posting here)

F_x = Fcosθ
F_y = Fsinθ

The Attempt at a Solution



6ca5e8152f0c14967495a8a01c2ab9a4.png




I thought it would just be either 100 N (the same as the northwest force 120° from x-axis) or it would be something involving the Pythagorean Theorem (100^2 + f^2 = 150^2 or 100^2 + 150^2 = 150^2)


Anyone? This is urgent. My whole class is confused.
 
Last edited:
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Since it's moving at a constant velocity, what is the sum of the forces on the object?
 
Pythagorean said:
Since it's moving at a constant velocity, what is the sum of the forces on the object?
zero
 
And the x and y directions are independent. So you have two equations, two variables, yeah?
 

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