Physics Review for the FE Exam
Physics concepts form the foundation of all engineering disciplines. The FE exam tests your ability to apply fundamental physics principles to engineering problems. This review covers the key physics topics you need to master, with emphasis on how they appear in exam questions.
Classical Mechanics
Newton's Laws of Motion
Newton's three laws are the basis of classical mechanics and appear throughout the FE exam:
- First Law (Inertia): An object at rest stays at rest, and an object in motion stays in motion with the same velocity, unless acted upon by a net external force.
- Second Law: F = ma. The net force on an object equals its mass times its acceleration. This is the most-used equation in mechanics.
- Third Law: For every action, there is an equal and opposite reaction.
Work, Energy, and Power
- Work: W = F * d * cos(theta), where theta is the angle between the force and displacement vectors. Work is a scalar quantity measured in joules (J) or foot-pounds (ft-lb).
- Kinetic energy: KE = (1/2) * m * v^2
- Potential energy: Gravitational PE = m * g * h; Elastic PE = (1/2) * k * x^2
- Conservation of energy: In a closed system, total energy is conserved. KE1 + PE1 = KE2 + PE2 (for conservative systems).
- Power: P = W/t = F * v. Measured in watts (W) or horsepower (hp).
Momentum and Impulse
- Linear momentum: p = m * v. Momentum is conserved in the absence of external forces.
- Impulse: J = F * delta_t = change in momentum. Used in collision and impact problems.
- Elastic collisions: Both momentum and kinetic energy are conserved.
- Inelastic collisions: Momentum is conserved; kinetic energy is not.
Rotational Mechanics
- Torque: tau = r * F * sin(theta) = I * alpha, where I is moment of inertia and alpha is angular acceleration.
- Angular momentum: L = I * omega, where omega is angular velocity.
- Rotational kinetic energy: KE_rot = (1/2) * I * omega^2
- Moment of inertia: Depends on mass distribution. Know values for common shapes (disk, rod, sphere) or look them up in the reference handbook.
Electricity and Magnetism
Electric Fields and Forces
- Coulomb's law: F = k * q1 * q2 / r^2. The force between two point charges is proportional to the product of their charges and inversely proportional to the square of the distance between them.
- Electric field: E = F / q = k * Q / r^2 for a point charge. The field points away from positive charges and toward negative charges.
- Electric potential: V = k * Q / r. Work per unit charge to bring a test charge from infinity to the point.
DC Circuits
- Ohm's law: V = I * R. The most fundamental circuit relationship.
- Series resistors: R_total = R1 + R2 + R3 + ...
- Parallel resistors: 1/R_total = 1/R1 + 1/R2 + 1/R3 + ...
- Kirchhoff's voltage law (KVL): The sum of voltages around any closed loop is zero.
- Kirchhoff's current law (KCL): The sum of currents entering a node equals the sum leaving.
- Power in circuits: P = V * I = I^2 * R = V^2 / R
Magnetism
- Magnetic force on a moving charge: F = q * v * B * sin(theta)
- Magnetic force on a current-carrying wire: F = I * L * B * sin(theta)
- Faraday's law: An induced EMF is produced when the magnetic flux through a circuit changes.
Waves and Optics
- Wave speed: v = f * lambda, where f is frequency and lambda is wavelength.
- Sound waves: Longitudinal waves through a medium. Speed depends on the medium properties.
- Light: Electromagnetic waves that travel at c = 3 x 10^8 m/s in vacuum.
- Reflection: Angle of incidence equals angle of reflection.
- Refraction: Snell's law: n1 * sin(theta1) = n2 * sin(theta2).
Units and Dimensional Analysis
Physics problems on the FE exam often involve unit conversions. Key unit relationships:
- 1 N = 1 kg * m/s^2
- 1 J = 1 N * m = 1 kg * m^2/s^2
- 1 W = 1 J/s
- 1 Pa = 1 N/m^2
Always carry units through your calculations and verify that your final answer has the correct units.
Physics is not just a standalone section on the FE exam; it is the language that all engineering topics are built upon. A strong physics foundation makes every other topic easier to understand and solve.