Chapter 5: Further Applications of Newton's Laws: Friction, Drag, and Elasticity

deformation

change in shape due to the application of force

Drag force

found to be proportional to the square of the speed of the object; mathematically where C is the drag coefficient, A is the area of the object facing the fluid, and p is the density of the fluid

Friction

a force that opposes relative motion or attempts at motion between systems in contact

Hooke’s Law

proportional relationship between the force on a material and the deformation it causes

Kinetic Friction

a force that opposes the motion of two systems that are in contact and moving relative to one another

magnitude of kinetic friction

where u_k is the coefficient of kinetic friction

magnitude of static friction

where u_s is the coefficient of static friction and N is the magnitude of the normal force

shear deformation

deformation perpendicular to the original length of an object; where S is the shear modulus and F is the force applied to perpendicular to L₀ and parallel to the cross-sectional area A

static friction

a force that opposes the motion of two systems that are in contact and are not moving relative to one another

Stoke’s Law

where r is the radius of the object, n is the viscosity of the fluid, and v is the object’s velocity; gives drag force for small objects moving in a denser medium

strain

ratio of change in length to original length; a unitless quantity

stress

ratio of force to area; measured in N/m²; equals to Y x strain

tensile strength

the breaking stress that will cause permanent deformation or fraction of a material

Relationship between the deformation and the applied force

where Y is s Young’s modulus, which depends on the substance, A is the cross-sectional area, and L₀ is the original length.

Relationship of the Change in Volume to other physical quantities

where B is the bulk modulus, V₀ is the original volume, and F/A is the force per unit area applied uniformly inward on all surfaces