Physics Friction Homework: Normal Force on 80kg Object

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Homework Help Overview

The problem involves calculating the normal force acting on an 80 kg object being pulled at angles of 50 degrees upward and 70 degrees downward with a force of 4000 N. The context is within the subject area of mechanics, specifically focusing on forces and their components.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants discuss the calculations for the normal force in both scenarios, with some suggesting the use of trigonometric functions to resolve the forces. There are questions about the correct application of sine and cosine in the context of the angles given. Some participants express confusion regarding the setup of the problem and the implications of pulling the object at an angle.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the problem. Some have provided calculations while others are questioning the assumptions made regarding the angles and the nature of the forces involved. There is no explicit consensus yet, but guidance has been offered regarding the use of free body diagrams and the effects of the pulling force on the normal force.

Contextual Notes

Participants note that the object is not on an incline, which raises questions about how to approach the problem. There is also mention of potential confusion regarding the direction of the angles and their impact on the calculations.

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Homework Statement


Find the normal force on an object, 80kg, which is being pulled up by a force of 4000N at an angle of: A) Up at 50 degrees. B) Down at an angle of 70 degrees.


Homework Equations


Fw = mg
Fsinx
Fcosx

The Attempt at a Solution



A) Fn = 784 - 4000sin50 = -2280 = 2280N


B) Fn = 784 + 4000sin70 = 4543N

Is this correct?
 
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part B would have to be sin(-70) since it is below, correct?
 
But did you notice that I added instead of subtracted the 2nd one?
 
Okay, well as I understand it for part A normal force is equal to mgcos50 degrees. I don't think you have to multiply anything but gravity by your mass.

Thus, n=mgcos: n=(80kg)(9.8 m/s^2)*cos(50)
 
It is not on an incline. it is being pulled up at an angle.
 
I can't picture anything being pulled up at an angle without being on an incline so I'm probably not the person to be trying to help. :/ Sorry
 
Have you tried drawing a free body diagram? What is the Normal force equal to? In part (a), is the pulling increasing or decreasing the normal force? In part (b) is the pulling increasing or decreasing the normal force?
 

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