Kinesiology Recording for Unit 2

Force, Weight, Mass, and Biomechanics Basics

• Force in physics

  • Force is a push or pull on a body and is a vector (has both magnitude and direction).

  • Mathematical relation: \mathbf{F} = m \mathbf{a}

  • The right-hand side uses mass (kg) and acceleration (m/s^2); force is measured in Newtons (N).

  • Free-body diagrams (FBD): a system isolated from its surroundings; draw all forces acting on it. For most problems, the weight is always present; other forces come from the problem setup (e.g., contact forces, friction, air resistance, applied forces).

• Mass vs. Weight

  • Mass is a measure of how much matter an object contains; in our course, mass is in kilograms (kg).

  • Weight is the gravitational force on a mass: W = m g with g \approx 9.81\ \mathrm{m\,s^{-2}} on Earth.