Ken Vos

Cheat Sheet / Updated 02-25-2022

Biophysics is the union of biology and physics. Physics is the study of the laws that the natural universe obeys, whereas biology is the study of life. Biophysics is an attempt to understand the laws that govern biological systems from the atoms and molecules within biological organisms to the environment. Biophysicists use the laws, techniques, and tools from physics and apply them to biological systems. This Cheat Sheet can help you in your biophysics class or wherever else your exposure to biophysics takes you.

Article / Updated 03-26-2016

Biomechanics, which is the study of the interaction of biological organisms with their surroundings, is an important area of biophysics. A solid understanding of biomechanics is important for people interested in kinesiology, physiotherapy, occupational therapy, and bioengineering. Biomechanics also deals with the small objects, such as the interaction of cells with their surroundings. Solving problems in biomechanics involves three important steps: Draw a figure, graph, or free-body diagram, even if a picture is provided. Visualizing what you know is a very important first step. Make lists and tables of what you know. Having a clear picture of what you know makes it easier to plot a path to the solution. Apply the appropriate physical principle. Some of the important concepts in biomechanics are The three fundamental types of energy used in biomechanics are kinetic energy, potential energy, and heat energy. The other two fundamental types of energy (not used in biomechanics) are mass energy and electromagnetic radiation. The connection between forces, torques, work, and power. The work-energy theorem equating the change in the kinetic energy to the net work done. The conservation of total energy, which means you can’t create or destroy energy. The conservation of (linear/angular) momentum in an isolated system. Conservation of linear momentum means the velocity of the center of mass is either zero or constant. Newton’s three laws of motion, which tell you how forces influence objects and change their motion. Kinematics gives the relationship between position, velocity, and acceleration, which allows you to describe the motion of an object without worrying about what is causing the motion.

Article / Updated 03-26-2016

Gasses and liquids are considered fluids. If you have ever watched smoke rise from a fire or a stick float down the river, you can see the way the fluid moves can be very complicated. The good news is that not all the types of motion of fluids are complex and complicated, but some types of motion can be modeled and well understood. The description of how fluids move is important in many areas of biophysics. You may be interested in understanding the motion of air within a person’s lungs, the motion of blood within the body, or the flight of birds to mention a few situations. For example, companies put a lot of research into developing the sharkskin swimsuit. These swimsuits are made of special materials and designed to reduce the drag between the swimmer and the water. The result: Most of the swimmers in international competitions wore the swimsuits by 2008. Swimmers wearing these swimsuits broke more than a hundred world records during the 2008–2009, which caused the International Swimming Federation to ban their use in 2010. When a biophysicist studies a fluid, he or she needs to determine the properties of the fluid, such as which forces are dominant and the type of fluid under consideration. Ask yourself these questions when determining the properties of a fluid: Is the fluid stationary (static) or moving (dynamical)? Is the viscosity of the fluid important (viscous fluid) or not (nonviscous fluid)? Is the fluid Newtonian or non-Newtonian (and what type of non-Newtonian fluid)? If the fluid is viscous and moving (dynamical), is the motion chaotic (turbulent) or non-chaotic (laminar flow)? What forces and laws are relevant? Some of the forces and laws relevant for fluids are The cohesive force, adhesive force, surface tension, and Laplace’s law Pascal’s principle, Archimedes’ principle, and the buoyancy force Continuity equation (conservation of mass), Bernoulli’s equation (work-energy theorem for fluids), and Poiseuille’s law (the net work done on the fluid is zero). Some of the forces and laws relevant for objects within a fluid are The drag force, which is proportional to the speed (liquid resistance) or speed squared (air resistance) Diffusion equation and Fick’s law Osmosis and osmosis pressure Michaelis-Menten kinetics

Article / Updated 03-26-2016

The ability of people to produce and hear sound is a very important part of everyday lives. Biophysics tells you what the properties of waves are, and it tells you that sound is a longitudinal pressure wave (in air) that is produced by mechanical vibrations. Biophysics also tells you how people can produce pressure waves for communicating with others and for singing. In addition, biophysics allows you to understand how people receive and analyze the pressure waves absorbed by the ear. The body has five senses, hearing being one of them. Your ear allows you to hear the pressure waves produced by others and any noise in the frequency range of 20 hertz to 20,000 hertz. Even though your ear can hear over such a large range of frequency, the human voice uses only the frequency range from about 100 hertz to 3,000 hertz. The pressures waves in air can be split into three categories, based on human hearing, as follows: Infrasound: Pressure waves with frequencies below 20 hertz. Some animals, such as whales, produce sound in this frequency range. Sound or acoustic: Pressure waves in the frequency range of 20 hertz to 20,000 hertz. This is the range of frequencies that the human ear can detect. Ultrasound: Pressure waves with a frequency greater than 20,000 hertz. Some animals, such as bat,s use this type to hear; it’s also used for ultrasound imaging.