Lesson Notes By Weeks and Term v5 - Grade 12

Lesson Video

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Performance objectives

• Define work, energy (kinetic & potential), and power, with their SI units.
• Calculate work done by a constant force, including at an angle.
• Apply the work-energy theorem to solve problems.
• Calculate gravitational and elastic potential energy.
• Calculate power as the rate of work done.

Lesson summary

This week, we delve deeper into the concepts of work, energy, and power within the realm of mechanics. These concepts are fundamental to understanding how forces cause motion and how energy is transferred and transformed in various systems. This is incredibly important in many aspects of South African life, from understanding how our power stations generate electricity to how vehicles move and function efficiently. Understanding these principles allows us to analyze the efficiency of machines, the impact of different energy sources, and even the safety of our transport systems.

Lesson notes

2.1 Work Work is done when a force causes a displacement. It's a scalar quantity, meaning it has magnitude but no direction. The SI unit of work is the Joule (J).

Formula: W = F Δx cos θ W = Work done (in Joules) F = Magnitude of the force (in Newtons) Δx = Magnitude of the displacement (in meters) θ = Angle between the force vector and the displacement vector Important Notes: If θ = 0°, the force and displacement are in the same direction, and W = FΔx. If θ = 90°, the force and displacement are perpendicular, and W =

0. If θ = 180°, the force and displacement are in opposite directions, and W = -FΔx (work is done against the force, like friction).