Minimum force to overcome static friction

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SUMMARY

The discussion centers on calculating the minimum force required to overcome static friction on an inclined plane. The correct formula is established as F = 196sin30° - (0.7 * 196cos30), where 196 represents the weight (mg) of the object. The confusion arises from the direction of the forces involved, particularly the static friction force, which is μ mg cosθ acting up the ramp. The solution confirms that the net forces acting down the ramp must be equated to determine the correct force required.

PREREQUISITES
  • Understanding of Newton's second law (Fnet = ma)
  • Knowledge of static friction and its formula (F_friction = μ mg cosθ)
  • Basic trigonometry, specifically sine and cosine functions
  • Familiarity with inclined plane physics
NEXT STEPS
  • Study the application of Newton's second law in various physics problems
  • Learn about the role of static friction in inclined planes
  • Explore the derivation and application of the static friction formula
  • Practice solving problems involving forces on inclined planes with varying angles
USEFUL FOR

Students studying physics, particularly those focusing on mechanics, as well as educators teaching concepts related to forces and friction on inclined planes.

idllotsaroms
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Homework Statement


http://postimage.org/image/530mgjivr/

How come the solution states: (20)(9.8)(0.7cos30 - sin 30) isn't sin30 going in the positive direction? shouldn't the solution be Sin30 - .7cos30? Also, when solving these types of problems should I leave the mg part outside of the cos and sin area? Cause I got

"F = 196sin30° - (.7 * 196cos30)"

Homework Equations



Newtons second law
Fnet = ma

The Attempt at a Solution



N = 193cos30
F = 196sin30° - (.7 * 196cos30)
 
Physics news on Phys.org
If you solve the equation for
F and assume down the plane is positive, the solution is correct, although the conversion factor from Newtons to pounds was left out in error. You get the same result in your attempt, except for the sign error.
 
The static friction force is μ mg cosθ which acts up-ramp. The total force acting down-ramp is F + mg sinθ. Equate the two net forces to each other.
 

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