Grade 12 Physics Revision Document
This revision guide focuses on the core concepts of the South African CAPS curriculum
for Grade 12 Physics (Physical Sciences Paper 1) for Term 2.
1. Work, Energy, and Power
• Work (𝑊): Work is done on an object when a force is applied to it and the object
moves in the direction of the force.
𝑊 = 𝐹Δ𝑥cos𝜃
where 𝜃 is the angle between the force 𝐹 and the displacement Δ𝑥.
o If 𝜃 = 0∘ , 𝑊 is positive (energy is added).
o If 𝜃 = 180∘ , 𝑊 is negative (energy is removed, e.g., friction).
o If 𝜃 = 90∘ , 𝑊 = 0 J.
• Work-Energy Theorem: The net work done on an object is equal to the change
in the object’s kinetic energy.
1 1
𝑊net = Δ𝐾 = 𝑚𝑣𝑓2 − 𝑚𝑣𝑖2
2 2
• Conservative and Non-conservative Forces:
o Conservative Force: A force for which the work done is independent of
the path taken (e.g., Gravity).
o Non-conservative Force: A force for which the work done depends on the
path taken (e.g., Friction, Air resistance, Tension).
• Conservation of Energy: In the presence of non-conservative forces, we use:
𝑊𝑛𝑐 = Δ𝐾 + Δ𝑈
where Δ𝑈 = 𝑚𝑔(ℎ𝑓 − ℎ𝑖 ) is the change in gravitational potential energy.
• Power (𝑃): The rate at which work is done or energy is expended.
𝑊
𝑃= or 𝑃avg = 𝐹𝑣avg
Δ𝑡
Units: Watts (W).
This revision guide focuses on the core concepts of the South African CAPS curriculum
for Grade 12 Physics (Physical Sciences Paper 1) for Term 2.
1. Work, Energy, and Power
• Work (𝑊): Work is done on an object when a force is applied to it and the object
moves in the direction of the force.
𝑊 = 𝐹Δ𝑥cos𝜃
where 𝜃 is the angle between the force 𝐹 and the displacement Δ𝑥.
o If 𝜃 = 0∘ , 𝑊 is positive (energy is added).
o If 𝜃 = 180∘ , 𝑊 is negative (energy is removed, e.g., friction).
o If 𝜃 = 90∘ , 𝑊 = 0 J.
• Work-Energy Theorem: The net work done on an object is equal to the change
in the object’s kinetic energy.
1 1
𝑊net = Δ𝐾 = 𝑚𝑣𝑓2 − 𝑚𝑣𝑖2
2 2
• Conservative and Non-conservative Forces:
o Conservative Force: A force for which the work done is independent of
the path taken (e.g., Gravity).
o Non-conservative Force: A force for which the work done depends on the
path taken (e.g., Friction, Air resistance, Tension).
• Conservation of Energy: In the presence of non-conservative forces, we use:
𝑊𝑛𝑐 = Δ𝐾 + Δ𝑈
where Δ𝑈 = 𝑚𝑔(ℎ𝑓 − ℎ𝑖 ) is the change in gravitational potential energy.
• Power (𝑃): The rate at which work is done or energy is expended.
𝑊
𝑃= or 𝑃avg = 𝐹𝑣avg
Δ𝑡
Units: Watts (W).
