Ch 18: Heat and TemperatureWorksheetSee 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

Solution: When a car brakes, a brake pad is pushed firmly against a disk, which allows the wheels to slow down. The effectiveness of brakes is limited by something known as “fade” – a rapid drop in friction. In

Problem

When a car brakes, a brake pad is pushed firmly against a disk, which allows the wheels to slow down. The effectiveness of brakes is limited by something known as “fade” – a rapid drop in friction. In a typical brake pad, the friction surface should remain below 450°C to prevent fade. For all problems, assume that the air temperature is 23°C.

(a) For a brake pad 1.65 cm thick, with an area of 53 cm  2 and a thermal conductivity of 12 W/mK, what is the maximum heat current through the pad that won't cause fade? Assume that the same amount of heat leaks out of the sides of the pad as goes straight through it.

 

 

 

 

(b) For a disk 1.1 cm thick, with an area of 268 cm  2 and a thermal conductivity of 43.5 W/mK, what is the maximum heat current through the disk that won't cause fade? Assume that the amount of heat leaks out of the sides of the disk as goes straight through it.

 

 

 

 

(c) For a 2000 kg car going 30 m/s, what is the shortest stopping distance the car can achieve without inducing fade? Assume that the car has 4 uniform brakes.