# Chemical and Physical Foundations of Biological Systems Section: Content Category 4A

Translational motion, forces, work, energy, and equilibrium in living systems
The motion of any object can be described in terms of displacement, velocity, and acceleration. Objects accelerate when subjected to external forces and are at equilibrium when the net force and the net torque acting upon them are zero. Many aspects of motion can be calculated with the knowledge that energy is conserved, even though it may be converted into different forms. In a living system, the energy for motion comes from the metabolism of fuel molecules, but the energetic requirements remain subject to the same physical principles.

The content in this category covers several physics topics relevant to living systems including translational motion, forces, work, energy, and equilibrium. The topics and subtopics are below:

### Topic Level Key:

The abbreviations found in parentheses indicate the course(s) in which undergraduate students at many colleges and universities learn about the topics and associated subtopics. The course abbreviations are:

PHY = two-semester sequence of introductory physics

Please note topics that appear on multiple content lists will be treated differently. Questions will focus on the topics as they are described in the narrative for the content category.

### Translational Motion (PHY)

• Units and dimensions
• Vectors, components
• Vector addition
• Speed, velocity (average and instantaneous)
• Acceleration

### Force (PHY)

• Newton’s First Law, inertia
• Newton’s Second Law (F = ma)
• Newton’s Third Law, forces equal and opposite
• Friction, static and kinetic
• Center of mass

### Equilibrium (PHY)

• Vector analysis of forces acting on a point object
• Torques, lever arms

### Work (PHY)

• Work done by a constant force: W = Fd cosθ
• Mechanical advantage
• Work Kinetic Energy Theorem
• Conservative forces

### Energy of Point Object Systems (PHY)

• Kinetic Energy: KE = ½ mv2; units
• Potential Energy
• PE = mgh (gravitational, local)
• PE = ½ kx2 (spring)
• Conservation of energy
• Power, units

### Periodic Motion (PHY)

• Amplitude, frequency, phase
• Transverse and longitudinal waves: wavelength and propagation speed

To support your studies, see the following video tutorials below from the Khan Academy MCAT Collection. The videos and associated questions were created by the Khan Academy in collaboration with the AAMC and the Robert Wood Johnson Foundation.