Edexcel iGCSE Physics -4.1 Energy and Power Units- Study Notes- New Syllabus
Edexcel iGCSE Physics -4.1 Energy and Power Units- Study Notes- New syllabus
Edexcel iGCSE Physics -4.1 Energy and Power Units- Study Notes -Edexcel iGCSE Physics – per latest Syllabus.
Key Concepts:
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SI Units Used in Mechanics and Energy
In physics, all measurements must be expressed using SI units. Using correct units is essential for calculations, clear communication, and gaining full marks in examinations.
Required SI Units
| Physical Quantity | SI Unit | Symbol |
|---|---|---|
| Mass | kilogram | kg |
| Distance / Displacement | metre | m |
| Time | second | s |
| Speed / Velocity | metre per second | m/s |
| Acceleration | metre per second squared | m/s² |
| Force | newton | N |
| Energy / Work | joule | J |
| Power | watt | W |
Key Relationships Using These Units
- Force: \( \mathrm{F = ma} \)
- Speed: \( \mathrm{v = \dfrac{s}{t}} \)
- Acceleration: \( \mathrm{a = \dfrac{v – u}{t}} \)
- Work done: \( \mathrm{E = F \times s} \)
- Power: \( \mathrm{P = \dfrac{E}{t}} \)
Understanding Derived Units
- Newton (N): \( \mathrm{1\ N = 1\ kg\,m/s^2} \)
- Joule (J): \( \mathrm{1\ J = 1\ N\,m} \)
- Watt (W): \( \mathrm{1\ W = 1\ J/s} \)
These units are derived from the base units kilogram, metre, and second.
Key Idea
- Always use SI units in calculations.
- Correct units help identify correct formulas.
- Final answers must include units.
Important Exam Tips
- Convert all values into SI units before calculating.
- Do not mix units (e.g. km with m).
- Missing units can lose marks.
Example
A force of \( \mathrm{12\ N} \) acts on a mass of \( \mathrm{3\ kg} \).
Calculate the acceleration of the object.
▶️ Answer / Explanation
Use:
\( \mathrm{F = ma} \)
\( \mathrm{a = \dfrac{F}{m} = \dfrac{12}{3}} \)
\( \mathrm{a = 4\ m/s^2} \)
Example
An electric motor transfers \( \mathrm{600\ J} \) of energy in \( \mathrm{20\ s} \).
Calculate the power of the motor.
▶️ Answer / Explanation
Use:
\( \mathrm{P = \dfrac{E}{t}} \)
\( \mathrm{P = \dfrac{600}{20}} \)
\( \mathrm{P = 30\ W} \)