Dabour Hub EGEgyptian Curriculum 2026/2027
2 Properties of the static friction force

2 Properties of the static friction force

Point 2 of 8 — Lesson 1: Equilibrium of a Particle, Friction and Limiting Static FrictionQuestion bank: 3 questions (3 with pictures)

02 2 Properties of the static friction force

Properties

  • Direction: static friction F opposes sliding; it acts opposite to the direction in which the body tends to slide.
  • Magnitude: F equals the tangential (sliding) force that tries to move the body, and it stays equal to it as long as the body is balanced.
  • Growth: as the tangential force increases, F increases, until it reaches a maximum value that it cannot exceed.
  • At that stage the body is about to slide, and the friction is called the limiting static friction Fs.
  • Therefore 0≤F≤Fs.

Coefficient of static friction

  • The ratio between the limiting friction and the normal reaction is constant for two given surfaces. It is the coefficient of static friction μs: Fs=μsN⟺μs=FsN
  • It depends on the nature of the surfaces, not on the shape of the contact area or on the masses.
  • Use F=μsN only when the body is about to move; otherwise find F from the equilibrium equations.

📝 Question bank for this point

3 questions linked to this point only, 3 of them with pictures.