Calculating Friction Force from Velocity Equation

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SUMMARY

The discussion centers on calculating the friction force acting on a 12 kg box that slides to a stop from an initial velocity of +8.4 m/s over a distance of +13.8 m. The participant initially miscalculated the mass as 877 kg, leading to an incorrect friction force calculation of -2242.06 N. Upon correcting the mass to 12 kg, the participant successfully determined the acceleration using the equation v^2 = v(o)^2 + 2ad, resulting in an acceleration of -2.55 m/s². The negative sign indicates the direction of the frictional force opposing the motion.

PREREQUISITES
  • Understanding of Newton's Second Law (F=ma)
  • Familiarity with kinematic equations, specifically v^2 = v(o)^2 + 2ad
  • Basic knowledge of friction and its directional properties
  • Ability to perform unit conversions and basic arithmetic operations
NEXT STEPS
  • Study the concept of friction coefficients and their calculation
  • Learn how to apply kinematic equations in different scenarios
  • Explore the implications of negative forces in physics
  • Investigate real-world applications of friction in engineering
USEFUL FOR

Students studying physics, particularly those focusing on mechanics, as well as educators looking for examples of friction force calculations in practical scenarios.

mrphobio
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Homework Statement


A 12 kg box slides across the floor with an initial velocity of +8.4 m/s. It comes to a stop after sliding +13.8 m.

How much friction was present?


Homework Equations


f=ma v^2=v(o)^2+2ad


The Attempt at a Solution


I did the ''v^2" equation to find out what the acceleration was, so i could find out what F equaled in f=ma. I got -2.55=a. I plugged that into F=ma, F=877(-2.55), which then F=-2242.06. But can a force be negative? And also from there I'm completely lost.
 
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Frictional force will be negative if you choose the displacement as positive because it is acting opposite to the direction of motion.

Check your math. Where did you get 877 for the mass?? It says 12kg.
 
Well. There we go it worked. I have not a clue where I got that 877. Sometimes another pair of eyes helps a lot haha
 

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