Ch 13: Rotational EquilibriumSee all chapters
All Chapters
Ch 01: Units & Vectors
Ch 02: 1D Motion (Kinematics)
Ch 03: 2D Motion (Projectile Motion)
Ch 04: Intro to Forces (Dynamics)
Ch 05: Friction, Inclines, Systems
Ch 06: Centripetal Forces & Gravitation
Ch 07: Work & Energy
Ch 08: Conservation of Energy
Ch 09: Momentum & Impulse
Ch 10: Rotational Kinematics
Ch 11: Rotational Inertia & Energy
Ch 12: Torque & Rotational Dynamics
Ch 13: Rotational Equilibrium
Ch 14: Angular Momentum
Ch 15: Periodic Motion (NEW)
Ch 15: Periodic Motion (Oscillations)
Ch 16: Waves & Sound
Ch 17: Fluid Mechanics
Ch 18: Heat and Temperature
Ch 19: Kinetic Theory of Ideal Gasses
Ch 20: The First Law of Thermodynamics
Ch 21: The Second Law of Thermodynamics
Ch 22: Electric Force & Field; Gauss' Law
Ch 23: Electric Potential
Ch 24: Capacitors & Dielectrics
Ch 25: Resistors & DC Circuits
Ch 26: Magnetic Fields and Forces
Ch 27: Sources of Magnetic Field
Ch 28: Induction and Inductance
Ch 29: Alternating Current
Ch 30: Electromagnetic Waves
Ch 31: Geometric Optics
Ch 32: Wave Optics
Ch 34: Special Relativity
Ch 35: Particle-Wave Duality
Ch 36: Atomic Structure
Ch 37: Nuclear Physics
Ch 38: Quantum Mechanics

Concept #1: Equilibrium in 2D - Ladder Problems

Practice: A ladder of mass 20 kg (uniformly distributed) and length 6 m rests against a vertical wall while making an angle of Θ = 60° with the horizontal, as shown. A 50 kg girl climbs 2 m up the ladder. Calculate the magnitude of the total contact force at the bottom of the ladder (Remember: You will need first calculate the magnitude of N,BOT and f,S).

Example #1: Minimum angle and friction for ladder

Additional Problems
A uniform bar of mass M and length l is propped against a very slick vertical wall as shown. The angle between the wall and the upper end of the bar is θ. The force of static friction between the upper end of the bar and the wall is negligible, but the bar remains at rest (in equilibrium). If we take the pivot at the point where the bar touches the floor, which expression below is (Στ), where x is along the floor and y is along the wall? 1. ℓ (Fwsinθ + Mg/2 cosθ) = 0 2. ℓ (Mg/2 cosθ − Fwsinθ) = 0 3. ℓ (Mg/2 − Fw) = 0 4. ℓ (−fssinθ − ncosθ) = 0 5. ℓ (Mg/2 + Fw) = 0 6. ℓ (Fwsinθ − Mg/2 cosθ) = 0 7. ℓ (−Mg/2 cosθ − Fwsinθ) = 0 8. ℓ (fssinθ − ncosθ) = 0 9. ℓ (Fwcosθ + Mg/2 sinθ) = 0 10. ℓ (Fwcosθ − Mg/2 sinθ) = 0 
A ladder is leaning against a smooth wall. The friction between the ladder and the floor holds the ladder in place. Determine torques about the pivot point P. Let τCCW and τCW represent counterclockwise and clockwise torques about point P (the base of the ladder), respectively.
In the figure, a ladder of weight 200 N and length 10 meters leans against a smooth wall (no friction on wall). A firefighter of weight 600 N climbs a distance x up the ladder. The coefficient of friction between ladder and the floor is 0.5. What is the maximum value of x if the ladder is not to slip?A) 6.28 mB) 6.04 mC) 8.44 mD) 3.93 mE) 5.00 m
An 80-kg man is one fourth of the way up a 10-m ladder that is resting against a smooth, frictionless wall. If the ladder has a mass of 20 kg and it makes an angle of 60° with the ground, find the force of friction of the ground on the foot of the ladder.a. 7.8 x 102 Nb. 2.0 x 102 Nc. 50 Nd. 1.7 x 102 N