How do I calculate the mass of a moving object?

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SUMMARY

The discussion focuses on calculating the mass of a couch being pushed with a force of 350 Newtons at an angle of 30 degrees below the horizontal, with coefficients of static and kinetic friction of μs = 0.4 and μf = 0.3, respectively. The correct approach involves applying Newton's second law (F = ma) and resolving forces, particularly the force of static friction (Fs = μsN) and the normal force (N = mgcosθ). The initial attempt at solving the problem contained errors in force resolution and misinterpretation of the equations, leading to incorrect conclusions about the mass of the couch.

PREREQUISITES
  • Understanding of Newton's laws of motion
  • Knowledge of static and kinetic friction coefficients
  • Ability to resolve forces into components
  • Familiarity with trigonometric functions in physics
NEXT STEPS
  • Review the application of Newton's second law in two-dimensional motion
  • Study the concepts of static and kinetic friction in detail
  • Learn how to resolve forces using trigonometric functions
  • Practice similar physics problems involving inclined planes and friction
USEFUL FOR

This discussion is beneficial for physics students, educators, and anyone interested in understanding the principles of force, motion, and friction in practical scenarios.

Joseph Hotto

Homework Statement



Someone mistakenly threw away a lovely couch, and you decide to take it back to your apartment. You push it with a force of 350 Newtons and at 30 degrees below the horizontal at 2 m/s. The coefficents of friction are μs = 0.4 and μf = 0.3. What is the couch's mass?

Homework Equations


Fs = μsN
N = mgcosθ
F = ma

The Attempt at a Solution


Fs = (0.4) (350 N)
= 140 N <- Force of static friction
ΣFx = (350) = (2m/s) * M + 2 (0.4) * M - 2(0.3 M)
350N = mg (cos(330 degrees)
350 = 0.866 mg
 
Physics news on Phys.org
Reconsider your calculation of the force of friction.
The quantity (2 m/s)*M is not a force. The entire equaiton for ΣFx is incorrect.
 

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